"Random" .net application errors

Once a month or so our users see a flurry of error messages from our .net app. The .net app is a piece of middle tier software that solicits input from users, makes a call to backend data base for data, then processes the data.

The messages persist for a day or two and then virtually disappear.
Environment: MS Windows 2008, .net application using BlueFinity connector and SyncFusion objects.

Was wondering if anyone may have any ideas as to what could cause this. We have MS Updates turned off and no other changes have been made to the server or the backend db. Here are some of the messages we are seeing.
1, Unexpected Error: Index was out of range. Must be non-negative and less than the size of the index
2. Unexpected Error: Input string was not in a correct format
3. Unexpected Error: Index was outside the bounds of the array
4. Unexpected Error: Value Close() cannot be called while doing createhandle()

We do not have any on-site .net expertise as the app was written by a 3rd party, any ideas for debugging the cause would be appreciated.
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David Johnson, CD, MVPOwnerCommented:
do you have the source code? you are going to need that and or a debug version of the code. and a debugger and the .pdb files.
Éric MoreauSenior .Net ConsultantCommented:
Randomness does not exist in applications!

I would start by adding Try ... Catch to my application to be able to detect where the exceptions are raised. All but the last seems very easy to fix when you know where to look at!

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Gautham JanardhanCommented:
Without code it would be hard to figure out whts wrong. Where did you get these errors Are they logged? Id so do they have stack trace?
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