I seem to have a larger memory leak on my current ubuntu System

After reporting strange Eclipse memory errors ( https://askubuntu.com/questions/148998/eclipse-constant-different-out-of-memory-errors ) I started to get 'Not enough Memory' error messages in my console today - while doing simple tasks like typing in sudo -s - or even - free -m

Typing in 'free -m' repeadetly showed me how my RAM quickly goes up from 700M to 900M, growing up to the size of 2000M in a few seconds (after freeing up memory with echo 3 > /proc/sys/vm/drop_caches )

Eclipse isnt the cause, I completly killed the process and the ram still was going up. Is there any way to detect where the leak is coming from? I cant even update my system anymore, since apt-get update fails (probably because it's out of memory)

Using Ubuntu 11.10