Kubuntu uses too much memory. What is the cause?

[Alvin]

My computer has 2GB ram. After running Jaunty for a while (an hour and up), 
the swap starts to fill and things start to get slow.

$ free -m
             total       used       free
Mem:          1978       1944         33
-/+ buffers/cache:        621       1356
Swap:         1906        759       1146

Programs I'm running:
- Kontact
- Amarok
- Dropbox
- Konsole

Other that that, there's not much activity.
Now, I don't see this behaviour on other Kubuntu boxes. Is there a way to see 
what process is filling the swap?