Yep, same problem here...
I had setiathome running in the background which uses all idle time... therefore my cpu usage is always 100%. I noticed the machine was very sluggish so I shut down seti@home. The problem remained however, so I found out Gnotella was causing it... pitty... I like the program. It's just not really usable this way...

I understand that gnotella developers have enough bugs to deal with, but I would suggest giving this one a high priority. I can live with most bugs and love to test programs for bugs, but this is one that really 'bugs' me since it makes the whole computer unusable...

Except for this little one: keep up the good work guys! :-)