Hi,
Having been in this situation many times previously, your next step is to request an order for any further works. Trying to diagnose the problem remotely with limited rights is extremely time consuming and you may never be able to find the problem.
I would suggest an onsite visit (at the customers expense) so you can check the environment.

And as far as there shortcut testing is concerned it proves nothing as it was not the environment that caused the problem.

>I appreciate your suggestions, but unfortunately I'm extremly limited on what I can do on the customer's server -- the only thing that I've got access to is a shared folder on the server (I've no access to the server itself). And yes, I did ask pretty much the same sort of questions you suggest from the very beginning. Haven't been told exactly what OS the server is running, though from what I can tell it's Windows Server 2003.
>
>It wasn't until recently did I finally get the customer to perform a few tests exactly as I requested and not take "shortcuts". One of the tests I requested we perfrom from the start was to see if a copy made of the program files from the server on a local drive would exhibit the same problem. They would report that the copied files would work fine. However, in reality they didn't actually copy the files from the server, but from a completely different computer. Because the server in question was accessed through a WAN and the copy would've taken too long, so they copied the files from a computer that was on their LAN (and since both the server and that computer had the program installed from the same install disk, "it was the same thing" as I asked them to do, just much quicker). Another test I had suggested is to compare the contents of the program files from server and those that got installed on the local harddisk. I suggested using the FC command on the command line to do
>this. They would report that no differences were found. What they actually did was "shortcut" again, and perform a completely different task -- they simply compared directory listings.