I have ample space...after selecting for hibernation, i still
left with 1.8gb. i have a 40gb drive. Last time (about 3 months
back) when i used this hibernation feature, it works even with
500mb left in my drive.
It seems that the hibernation feature is corrupted. Because when i
choose to hibernate, the applet of the hibernating in progress
comes out and the computer hangs...like never move like that and
stays at hibernating in progress. 
Please help.