internet connect freezes
 

My internet connect freezes at random times.
I have an ISN USB terminal adaptor and frequently it will try to disconnect but just get stuck disconnecting, the only way to fix it is reboot the mac. I don't think it is the terminal adaptor because I have 2 different ones and they both freeze the same. I get message in staus bar top right that it is disconnecting, but It wot get any further.

G5 dual 18ghz/1Gb Ram OX 10.3.2
(although it did same on older g3 300mhz/320mb ram 10.2.8)

draytek and hermstedt isdn USB TA's

Anyone throw an kight on the subject?

I've been getting the same problem with standard dial-up on a pb running 10.3.2
Rebooting fixes it for a while then it happens again and again.
Hopefully someone out there can suggest a fix