[psyklic]

I've had this happen many times on random users' systems. If the user is nice enough to work with you (and they were in my case since they were caught pre-deployment in contract work), you can often ask them to try new things with a dev build for instance.

The main key is to reproduce the errors on your system, so just try a bunch of wacky things like different screen resolutions, memory constraints, database configurations, etc. Continually look at the code and brainstorm what might cause that issue -- there are a limited number of code paths -- and try to cause the constraints in your code. It's definitely very specific to the individual situation.