I got a similar problem. I installed a completely fresh, legal version of GTA. Put the ~Removed, Piracy. - TheRock~ on it and installed SAMP.
When I try to join Argonath RPG, the game crashes as soon as the loading screen finished. I dont know what to do.
SAMP and GTA's exe are on admin and compatibility mode. The installation folder is in "C:\Games\Rockstar Games\GTA San Andreas\"
Also yesterday I was able to play for hours easily. I changed nothing and today I couldnt join the server without crashing right after the loading screen.
I am re-installing my GTA right now. This time to "C:\Games\GTA San Andreas\".
EDIT: Installing it in "\Games\GTA San Andreas\" didnt help, but somehow renaming the folder to "GTA San Andreas 2" fixed the whole problem... strange shit, but ok. Mines fixed.