"networking error" w/itunes, software update

This seems to be a problem I'm having throughout my system with iTunes, software update, etc. I CAN connect to the internet from the dock, but iTunes gives me "a networking error has occured (-1001.) Make sure you can connect to the internet, then try again." Safari has been down, but I reset Netscape as my default browser. Network diagnostics say everything looks good, but I'm still having problems. Any advice would be much appreciated

thanks,
Lauren

PowerPC G4 Mac OS X (10.4.7)