Do you have anti-spyware/anti-adware software? If you do and did a scan prior to the appearance of the problem, then it could be that you deleted something that you shouldn't have with it.

__________________
iMac G4 OSX 10.3.9
RAM 256MB
LW 4.10.5 Basic
ADSL anything from 3 to 8Mbps/around 1024kbps

"Raise your can of Beer on high
And seal your fate forever
Our best years have passed us by
The Golden Age Of Leather"
-Blue Öyster Cult-