Any of the more recent trainers will do a call home to verify the trainer and to retrieve a random trainer advertisement ( for instance, new at cheathappens: grimrock trainer ).

If I alt-tab to any other window, or make the trainer lose focus while it's calling home... it will crash.
As a developer, this looks to me like your requesting focus to an object while the owner-window does not have focus, in languages like delphi/c++(older .net framework or non .net ) this would result in an error. So I'm guessing that is what's going on.

To illustrate, I made a video and posted it on youtube,
Link

This is what you see me doing:
- I open the Risen 2 trainer and let the window lose focus right away
- Trainer crash

- I open the Risen 2 trainer again and wait for the advertisements to load
- No crash

- I open the stronghold 3 trainer and wait for the advertisements to load
- No crash

- I open the stronghold 3 trainer again, and let the window lose focus right away
- trainer crash

- I open the Supreme Commander 2 trainer ( older trainer-framework) and let it lose focus right away
- no crash

Sounds to me like a simple bug in your base-trainer framework, and I would love a fix. (win7 sp1 ult. 64bit )
Feel free to contact me for more details

[Edited by cainite, 5/5/2012 6:41:12 AM]