I'll try that this evening as it goes. Part of me's thinking just to wipe the whole computer and start from scratch, at least i'll have a cleaned up computer as well. Surely the wireless adapter is working ok if my ps3 can connect to the laptop wirelessly as well?

I hate computers!

A noticable drop in performance is usually caused by interference from a another wireless access point within the vincinity of yours operating on the same channel. I would say a neighbour nearby has recently set up wireless and its running on the same channel as yours. Even if you can't see their access point it doesn't mean it's not there. They may SSID Broadcast disabled for extra security or it may be just outside the range of your wireless adaptor but its signals would still interfere with your wireless.

If you're using the default SSID of NETGEAR you should change it and you should also try changing the channel the wireless router operates on to channel 3 for example. The default for most netgears is channel 11.