[link|http://kbserver.netgear.com/kb_web_files/n100772.asp|This] netgear page talks about some issues with SP1 that are supposed to be fixed with SP2.
Does it only happen with XP?
Have you tried an older version of the [link|http://kbserver.netgear.com/products_automatic/WGT624v1.asp|firmware]?
I'll bet you've already considered these things. Sorry I can't help more.
Cheers,
Scott.