You know, I used to see that window way too often before, but I managed to find the cause and the problem.
Do you have an nVidia GFX card? Does your motherboard has an onboard audiochip? If so, you may be suffering from the same issues my computer was having.
Check this support thread.
http://www.evga.com/support/faq/afmmain.aspx?faqid=59211I used to have a lot of HL2.exe has crashed (with crazy loud sound loop) after playing for like 20min. Since I followed the instructions above, I don't have this problem anymore. Maybe it can help you guys too.
If it doesn't, there might be some other things you could try...