Strange problem my Minecraft launches /w java 32bit not java 64bit

first off I run a server in which about 16 players are playing, everyones pc runs the game on java 32bit but 3 of players pc's keep crashing on java 32 bit with the out of memory error.  Strange thing is as soon as i try to use 64 bit java it crashes log reads perm gen out of memory. Game runs perfect on my pc 32bit java no crashes. its the other folks who have problems with 32bit crashing. But none of us can use java 64 bit the game crashes at the mojang screen.

my server is 1.6.4

wow you are the man thank you so much lol. Now I can work on updating to 1.7 while everyone still can play