RE-Installed New 6.06 (Video Problem)

[Richard]

After having some weirdness during the upgrade, had to re-install ubuntu 
6.06.

Now my monitor Nec LCD1700V is not set at the correct res.
1280 x 1024 @ 75hz,

its 1024 x 768 @ 60hz, there are none setting higher.
could some please tell me how to fix this problem.
using a nvida Geforce2 Mx/Mx 400.

Thanks +++++
Rich