On my Acer laptop wit ATI Xpress 1100 I have a native resolution of 1280 x 800, and Linux Mint 8 (of the Ubuntu family) offers that resolution without a problem.

However, a few days ago I connected my laptop to my TV, and since then the correct resolution setting has been LOST.
It doesn't appear anymore in the Display settings and so I had to choose a lesser resolution - I am now looking at a less sharp screen!
Probably some kind of configuration file is corrupted, but which one, does anyone know? How can I delete it? I hope that I don't need to reinstall...

The display settings are stored in: /etc/X11/xorg.conf
You should try removing it (but please make a backup), then in most cases the screen resolution will be detected automatically.

YESS.
That worked!

Actually, the display settings must be stored somewhere else for no new xorg.conf file was made. But evidently that file took priority over the (hidden) correct settings.

Thanks a lot!