Dota Problem


I have and eMac G4 800MHz with 512 mb RAM

I play Warcraft III and i mostly play a custom game in it called dota. For some reason my computer doesn't play the game sometimes. It shows the load screen and as soon as it finishes it quits out of the game (not out of battlenet) and i mess up the game. It is not my internet connection i know this for sure and it only happens some of the time. Could this be not enough RAM, too slow of a processor or a bad graphics card (im not sure what card i have but its not great)?

Please give me some ideas on how to fix this problem as it is very frustrating

I would blame it on Warcraft III. Since OS X was updated to 10.3 (I think it was 10.3) Warcraft is anything but stable. It crashes all the time, so I do not bother anymore about playing it. Blizzard always says their programmers are on the hunt for this bug, but I seriously doubt that (after all, this problem occured over 1 year ago...)
I run Warcraft III on 10.2.8 and Warcraft doesnt crash. The program doesn't crash it just quits this one specific game as if i went to menu and clicked "quit mission" but does this right at the start.