Problems with resolution

Hi,
after I tried to fix my Brigantia suspend issue as described on another topic on this site I brorked somehow my resolution settings.
The problem appeard after I added the "nomodeset" in /etc/default/grub and ran "update-grub".
Now my maximum resolution is 1024x768 instead of 1366x768.
Any idea how to fix this ?

Thanks in advance.

*sorry for my english.