Abe try to clear your cookies (tools->etc), may fix the new post problem.
I take it the game is stuck (no windows errors etc)? If so on windows xp press ctrl alt del (task manager will show up in the background). It should open the process tab by default. Type bfv (so the process bfvietnam.exe is selected) and press alt+P. Normally that should exit battlefield vietnam if you can't see the taskmanager.
Don't have much ideas about the crash except reinstall(latest patch).