I'll be online just fine, then I'll get disconnected for a couple minutes, then all will be fine once again.
It's happened to my laptop, work laptop, and 360 for sure - the PS3 is a maybe. In fact, I'll be disconnected from the party but remain in the game sometimes, which is really bizarre. I thought at first that it had to do with how many wifi devices were connecting, but now I'm not so sure. I went ahead and strung a wire to the living room for the 360, and it's still being somewhat wonky. I lost voice chat entirely the other night. I rebooted the router, and it was working fine last I checked.
It's just been happening WAY more often lately, and I'm wondering if the router is just dying. It's a NetGear I picked up... 4+ years ago? So probably due for replacement anyway. There's just not much new, and I don't really want to spend much on it. I see someone (Linksys?) finally has a gigabit router with wifi, but it's still only 4 port. Make that an 8 port and under $100, and I'm in. I'm thinking more of $50 limit this time, though.