This is most certainly a bug. Last time, I connected a Gateway 17" external monitor to my laptop at university, and it recognised it fine. Today, when I connected Dell 22" at work, Ubuntu kept recognising it as the Gateway monitor. I was trying to solve the problem by disconnecting the monitor, pushing "detect monitors" button again, but nothing worked, so I had to restart. One interesting thing is that it recognises Gateway after Dell without a problem, but not the other way around, as if it knows that Gateway will simply not take 1680x1050 resolution. It is irritating because I normally do not reboot the computer too often (once a week at most).

Any advice will be appreciated.