Bad applications does Bad stuff with you Memor. Today my Skype decide to flood my Memory. Lucky i notified this on the right time and was able to run killall -9 skype . But what left is a overfileld Memory and swap. For the Memory itself no problem, the kernel will empty it by demand. But for my older hard drive takes ages to get it back. So the best is it to empty it. The best way to do it: swapoff/swapon.
This take now a while but it will do the job.
When it's done re-enable it with