Losing screen resolution settings

Hi:

My preferred screen resolution is 1280 by 1024, as set in Display Properties > Settings. This has been stable for ages.

Recently, however, about 2 times out of 10, the screen comes up as 800 x 600.

There are two ways of putting it right (i.e. to 1280 x 1024): (1) obviously, by going to Display Properties and changing it to what it should be, and (2) by doing a restart which usually fires up at 1280 x 1024.

I've tried powering-down completely (i.e. disconnecting the computer from the mains), but that makes no difference: the screen resolution either comes up correctly or not.

The only thing that has happened between always okay and intermittently okay was a slight problem with a cup of coffee! [I know... that's bad... but I have been working with computers since 1969 and have only had two spills! Yeah... still bad!] Luckily, the coffee didn't penetrate into the guts of the computer and just filled up the ports in the top panel (i.e. phones, mic, firewire, usb). After drying them, I took the extra precaution of isolating them by unplugging their cables and have left them in this state.

I'd be very grateful for suggestions.

 

Many thanks... I'll give that a go.