This problem is caused by a serious malfunction called crappy computer.
You can try to fix this problem by:
a) closing all non-essential background programs while running planeshift
b) use a memory optimizer to sweep you memory before running planeshift
c) increase the size of your virtual memory
d) buy a new computer (not recommended)
e) have patience while turning, turns slowly (tap the keys, don\'t keep pressing them when the game freezes).
One of those things has to help; it would be helpful if you post your specs next time you have a problem.