Sometimes my N900 drives me mad with unresponsiveness and most of the time it comes from automatically, stupidly launched processes.
It pisses me off :/
For example, now, my device is with high load and processing because of hildon-thumbnailer.. I haven't put any new images on my N900, neither connected bia usb or so.. it just launched and made everything stops working good, even processes that should have more priority, like phone app.
Well, is there a way to stop these auto (dumb) start or change the nice/priority of these services?

install tracker-cfg, it lets you tweak the various indexers

Have a look at my second post here and see if it helps.

thanks guys, you both helped me out!