how come x apps when you drop the app down and bring it back up the app is some times blank and you half to kill it

my hardware is a p3-866 gforce 2 mmx 64 with a cold swap drive
and mandrake 9.0 or rhat 9 and lycoris build 64

is this a memory issue? my mandrake is a 10 gig and rhat is 40gig
and lycoris is 4 gig it just bothers me that the apps do that and when i make a short cut for x like the app gtkhx any hints would be helpful