Sapphire Radeon 9000 pro issue using catalyst drivers on win 2k or win xp

Hi all, I recently replaced my AIW Radeon with a Radeon 9000 Pro. When
Win 2k was installed, when ATI utils are loading after logon, the
monitor began to turn off and on for a couple of times, as if the card
is swapping to the second video output, that is not installed. The
same happened every time I clicked the ATI systray icon.
Last week I replaced Win 2k with Win Xp. Before installing the ATI
Catalyst drivers, the card seemed to work correctly, but with the
latest drivers the issues started again.
Did anybody encounter this issue? Is it a Catalyst drivers issue or is
related with my hardware (matherboard Abit KT7a-Raid)?
Thanks in advance for any help.

Gigiumba