ASP.NET Server error specific to one client computer, works fine on other computers!

I have to use a .NET ASP website to log time for a project, and the website works from some client machines but not others.
The machine that does not work gets a SERVER error NOT a client side error, and the error occurs on that machine with IE 10, Firefox, and Chrome. (Windows 7)
On another windows 7 machine the site works with no problem, same page, same login, and with IE 10 or Chrome (didn't try firefox).

Can someone suggest why a site would work for some machines and not others but the error would be a server error?

The server error is below.

Server Error in '/timesheet' Application.

Input string was not in a correct format.
  Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

 Exception Details: System.FormatException: Input string was not in a correct format.

Source Error:

 An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.  

Stack Trace:

[FormatException: Input string was not in a correct format.]
   System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) +7471287
   System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info) +119
   System.Convert.ToInt32(String value) +63
   Infragistics.WebUI.UltraWebToolbar.UltraWebToolbar.getRenderer() +444
   Infragistics.WebUI.UltraWebToolbar.UltraWebToolbar.OnPreRender(EventArgs e) +106
   System.Web.UI.Control.PreRenderRecursiveInternal() +80
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +842


Version Information: Microsoft .NET Framework Version:2.0.50727.4961; ASP.NET Version:2.0.50727.4955
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vtechdevAuthor Commented:
PS cleared the cache, cookies etc. Really strange since 3 different browsers fail on same machine, but error is server error.
The site has a login page and I enter my username and password, neither is numeric so that does not seem to be the source of the problem, following login it shows a time tracking page where I can log time, but this page never displays on the machine where the error is displayed, I get an error page with the content posted. On other machines with the same user login the time track page works fine and displays without error.
Jesus RodriguezIT ManagerCommented:
Check the language in the Regional Settings of this computer under the control panel to see if the configuration of the Numbers/Date/Keyboard is the same to the other computers?? Looks like is trying to do something on the code receiving a different format than expected.
Sudeep SharmaTechnical DesignerCommented:
Is the machine fully patched? Do you have all the .Net updates installed?

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vtechdevAuthor Commented:
Yes, I believe so, but how can the client machine cause an error on the server?
I have no idea about the server state, I'm just a user.
Jesus RodriguezIT ManagerCommented:
Did you check the regional configuration for the computer that is causing the error against the other ones that work ??
vtechdevAuthor Commented:
Hi Jesus,
I just checked and the computers that work and the one that does not have the exact same settings.
This is really weird.
Vikram Singh SainiSoftware Engineer cum AD DeveloperCommented:

(1) Are you sure you are sending same input to website on both of the servers?

Try copy paste same input on both servers from some file. Either there is something that is appended to input values.

(2) You can report this issue to website owner. Because I believe there code is not checking string value. They are directly trying to convert it into integer value. They will be able to answer you more properly.
Jesus RodriguezIT ManagerCommented:
I got this problem before and was my fault at the time of programing the sub. The program as is assume that the client will send the right date/time to the program and then I do the convert and other functions with the date/time but at the time of converting this to operate or save it to other places, give me and error. I solve that with setting the regional settings on the client as same as I expect to receive the data till I patch later the program.

 As Vikran said, try to contact the person that design the software or web page because must be the way that the application is receiving data from different clients and again, sorry for this but double check that the region configuration is the same for both machine (Machine that works and Machine that doesn't work see attached picture)
vtechdevAuthor Commented:
Hi Vikram, both send exactly the same data only a user name and password entered on login page. No numeric data exists in either one (Yes I know lousy security)
vtechdevAuthor Commented:
Hi Jesus,

I've already checked the regional settings both machines have exactly the same settings.
The party that owns the site does not seem to care because "It works fine for me!"
Of course the don't seem to care that the error clearly states there is an unhandled exception in their code that is causing the problem.
I'm sure you know the type.
Jesus RodriguezIT ManagerCommented:
Sorry to heard that my friend, Still there is people that doesn't care for a customer after the sale. You already follow all the steps to troubleshoot your end.

On the programming world I can tell you that
"Exception Details: System.FormatException: Input string was not in a correct format"

means that is trying to convert from one format to another and the receiving data that needs to be converted is not on the expected format that needs to be and that's why can not be converted. They need to check what are the receive data that will be converted no matter what will be the client configuration. At the end I hope that they don't respond like sometimes other vendors do (" Can not reproduce your issue")

As the last thing that I can suggest you check on Internet Explorer/Internet Options/General/Languages and see if your computer and the other one that cause the error, has the same language,
vtechdevAuthor Commented:
yes language is the same on both computers
Jesus RodriguezIT ManagerCommented:
Really don't know what to tell you but 100% sure that is not your end. Regarding the client browser, they need to verify the input data and the transformation that they must do. Is not in your end.

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