I own a 120GB Xbox Elite and use a wireless adapter to connect to Xbox Live. After reading a lot of 'fairly' common reports of the same issue that I am experiencing. I thought I would bring it to attention, that it isn't all 250GB Slim with built in wi-fi that are encountering this rather annoying issue as of late. At first I thought it could be my router at fault, but it isn't. I'm still connected to my PC, whilst the 360 will randomly disconnect from Live. I would say this problem has become more frequent over the past couple of days.
Once I am disconnected and resign back into Live. I instantly do the 'Test Xbox Live Connection' so I can then join my friends. If I don't do that, I won't be able to connect to my friends, which narrows it down to the NAT settings perhaps? When I can't join Xbox Live Party's, I use Reach to check my NAT settings and then I test my connection so I can join.
Maybe if I disconnect from wireless router and input the router key. Would you think this would cure the problem? Just a idea that I had.
P.S - Thanks in advance to any replies that I get. =D