I recently had this same problem, but only when running Windows (I'm on an Apple PowerMac, so I switch back and forth between running Mac OS X and Windows XP) and only during high traffic like BitTorrent downloads. I don't know if it was simply losing the connection, or if the router was somehow resetting (I can't see the lights from where I'm sitting). Anyway, I can't remember what led me to try this, but I unchecked the box for "Enable Auto Channel Scan" and made sure to set the channel to whatever number was currently in use (channel 9, in my case). It's only been a couple of days, but so far the connection has been stable since then, regardless of which OS is in use and even when downloading BitTorrents at full speed.
I don't know if this helps you at all, but I figured it was possibly worth mentioning. Couldn't hurt to try, right? (Famous last words...)
Oh btw, my hardware version is A2 and firmware version is 1.11. Also, I suggest keeping Visibility Status as "visible", as in my case invisibility only seemed to exacerbate the issue (or so it appeared).