Belkin 54g, Vista laptop & XP laptop

Hey, need a bit of advice on a couple of issues.

Firstly - for some reason my wireless network seems to go dead around 01:00am...and it's not every day, just sometimes. It seems to be just between the latop and router, as Xbox Live continues to work fine and the router itself shows the online light still...it can't be remedied by re-connecting, it can't be remedied by the remote access as you can't connect to the Belkin control panel...so the laptop has to be re-started and router re-set.
Any ideas?!

Secondly - I have two laptops running on the wireless network, mine on Vista and another on XP. For some reason when I enable UPNP on the router the XP laptop can't get internet connectivity from the network?

Bit of an amateur on all this so any advice needs to be pretty simplified! cheers