Should I be worried? XBLive & Overheating?

Okay, so I tried out XBLive a couple of nights ago (you know, using one of those 2-month trials) and started playing Star Wars Battlefront. About 5 minutes into a game (a connection rampant with lag, by the way), the game locked up. When I turned it off and booted back up to evox, the temp reading was at about 53 degrees Celsius. My system usually runs at about 49 degrees Celsius (having upped the fan speed to 65%). She (yes, my xbox is a "she") runs fine now and I played some other game for about 30 minutes and checked the temp again; it was about 49 degrees as normal.

So, I suspect overheating caused my crash, but what caused the overheating? XBLive? Sporadic lag? Highly populated game (the game was near full at 22(?) people)?

Doesn't XB employ an overtemp failsafe? An automatic power-down before fatal overheating?

Should I be worried? I'm just a little paranoid because I'm fairly sure I fried my first system.

At any rate, I guess I won't be going on-line with Halo 2 anymore...