Ibook grinds to a halt

Hey all,
My ibook g3 is suddenly grinding to a slow and painful halt. All of a sudden, stuff starts slowing down. At the moment i'm burning a cd in itunes and the mouse cursor is very very slow to move (previously it worked fine). Don't know if it's related, but the firewall on another computer on the network detected some access attempts shortly after i started the ibook. Anyway, is there any way that I can trace and destroy this latest weirdness?

Thanks for any responses.