>>>>No, I didn't copy .pdb file to the .bin on the customer machine. I will Google the .pdb type file to see what is the purpose of it; I really don't know. Thank you.
>>>
>>>Oh sorry Dmitry, I guess I should have elaborated. The .pdb files contain the debugging information, which normally don't get distributed, but in this case it looks like you might want to know.
>>>
>>>~~Bonnie
>>
>>Not a problem. I will have to try placing the .pdb file on the customer server to see if this is what will help me see the trace. Actually I believe I solved the problem that prompted me to start this thread in the beginning. But I need to learn (for some future cases) how to trace the program on customer site/server. Thank you, Bonnie.
>
>Hi Dmitry,
>
>I would be curious to learn about how did you solve the original problem. I'm guessing it's the Null exception problem you posted before, correct?

I created a separate Application Pool for my ASP.NET program. Initially my program was using Application Pool of the default web site. Once I set a separate Application Pool the error of the Null exception was gone (at least so far, in a few days nobody got this error). So I suspect that another application was "interfering" with my program by removing/clearing the cache. I really know nothing about how the Application Pool works but this is my WAG.