Why? Don't jump so fast to such "radical" solutions (it probably wouldn't help much too). It could be a firewall problem indeed, so go to Options and click Bug reports. There, click the button that will give you an example and scroll down to the part were it says "Recieved incoming this session". True indicates that everything is a-ok. False might be an indication that a firewall is behind your prob.

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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-