Random disconnects

I keep losing my connection, which is very frustrating when trying to play WoW and just as annoying when trying to surf ebay, look at my webmail page or do anything really. I'm using a Speedtouch 330 ADSL USB modem. I got it free from someone after my ethernet router modem died. They've never used it so it is brand spanking new. My ISP is Freedom2surf who I have never had any problems with regarding connectivity. I've switched off Zone Alarm and tried diffferent USB ports and it's still happening. I'm running on XP SP2.

Previously I was using 2 long ethernet cables that ran to the router modem which was by the phone socket. To enable the USB modem I had to run a line extension from my phone socket to where my PCs are. The fact it works some of the time tells me I did something right. I've enabled everything I can find to not drop the connection when idle but it still seems to do it. It seems entirely random though rather than after a set amount of time.

Weirdest of all was that when my girlfriend was chatting to someone on the phone it couldn't hold a connection at all. I thought the whole point of ADSL, other than the big pipe, ws that you could do both at once. Damn thing is acting like a dial up.