X and Fluxbox :: Display goes out of range

I am using ViewSonic VE710s monitor.

The suggested resolution is 1280 x 1024.

So I chose 1280 x 1024 24bits

After the installation, it runs XWindow, the screen blacks out and showing "out of range".

Then I tried 1024 x 768, its still showing "out of range".

Until I tried 800 x 600, then it works.

I wonder if its the frequency issue. But it cannot find a way to choose frequency during the installation.

Anyone knows what's going on?

Please let me know.

Thank you.

original here.