Exchange users randomly get prompted for their credentials

AremP,

What OS is your client running?

I have seen this before as well, but am not sure what the solution is just yet!  

all users are on Windows 7 Professional 64-bit.  They have had this new system in since October and have never had an issue.  It has been happening in the past month or so.

Close Outlook
Open C:\Users\YourUserName\AppData\Roaming\Microsoft
Delete all "Protect folder"
Restart outlook, give password again.

Try if this works out

You can also try Autodiscover troubleshooting steps
http://www.msexchange.org/articles_tutorials/exchange-server-2010/management-administration/exchange-autodiscover.html

These users are not mobile, their computers are stationary at the local network.  They are hardwired to the LAN (no wireless)

First check DC's are working fine. Are you able to ping DC regularly from Exchange and client machine

Yes, there is no issue with the domain controller.  The users have no other connectivity issues besides this one.

Check this
http://demazter.wordpress.com/2010/02/09/outlook-continually-prompting-for-username-and-password-2/

I was facing similar issue in my office but this is due to either the AD user account is locked or the password has expired

So once this problem happens again; check for these two things first.

May be the user saved his old password in IE, or other applications which make his acccount get locked.


Also to get more info on this; when this problem occurs; it happens to all users or to some users. If for all users then you have some global issues like you said auto-discovery or DCs; but if it happens to one or two then check the individual workstation i.e. Outlook profile, User profile, password exiry or locked out

I've been doing testing on one computer that has had this reoccurring issue.  I've wiped the email profile and created another one.  If further problems persist, I'll create a new profile.  It is not a global issue, just a random issue.

AremP,

I would take a look at the "blog link from amitkulshrestha, specifically the last part about kernel authentication mode.  I just checked my autodiscover server and that setting was missing.  

Great! That's a simple solution.  

fixed it myself