I also had a lot of crashes. I tried everything but had no succes. Than I reinstalled GP4 without any patch or add on. I ran it in win98 compatibility mode and had no crashes. After that I installed the official GP4-patch, also still no crashes. I than installed GPxPatch, the game still was very stable. After that I installed CSM and some mods -> the games started crashing so I went back to previous version (I made backup's of the complete GP4 folder after every change I made). Know I created my own 2007 mod which runs great without CSM! I know have a few GP4 folders on my HD:
GP4 2001 -> default GP4 season 2001
GP4 1994 -> The 1994 mod
GP4 2007 -> My own 2007 mod with tracks etc
So I dont use CSM anymore, I just have complete GP4 folders for each mod I play and my system is very stable!
I'm planning on creating also my own GP4 1991, GP4 1995 and GP4 2006 folder
But before I install anything I make a backup so that I can also go one step back.
Hope this helps a bit!