Vertical flicker on Hitachi LCD

Please advice!

Bought my "Hitachi CML175SXW B" LCD monitor a week ago.
Was using it on 75 Hz (checked all allowed 60, 70 and 75), digital cable (tried analog too), on Connect3D Radeon 9500 Pro. Everything was fine.

Yesterday (see the attached picture) strange vertical flickering started: a vertical band of about two inches wide, where the colors and picture are garbled and constantly changing.

It just started at the end of a working day, nothing was done to provoke it (no switching on/off, nothing plugged in...). But now sometimes it seems worse after switching the machine on, and then goes down, even disappears totally for up to a couple of hours, then comes again...

Flickering decreases at 70 Hz, decreases further at 60 Hz, sometimes disappears, then comes back after a while...

Also, the flickering can't be caught by PrintScreen (at least, I did not manage).
It seems to be the monitor and not the graphic card - I've tried to change to the onboard (SiS).

What shall I do? Am I missing something, or should it be replaced?

Thanks!

Mike