Thanks to everyone who replied.

If the power strip is to blame for sending a surge down the network cable
would it be because it is too far from an earth ground? It is on a normal 3
prong plug but the room that its in is more than 3 metres from the metre
box. Are there other points, besides the metre box, where the 3rd wire
reaches earth ground in a typical house wiring setup?

Also does anyone have any suggestions for a good whole-house surge protector
- good brands? expected pricing? any that can be installed DIY? And does
anyone know of any companies here in Sydney Australia who do installations
or sell these things?

Thanks

Tim Edwards