Monitor doesn't work anymore since updating to Snow Leopard

[KaiXXX]

Hi,

I bought the Snow Leopard update a couple of days ago and installed it on my MacPro (Early 2008, 8core, ATI Radeon HD 2600 XT). Since that day my second Monitor doesn't work anymore when connected to the DVI port. It's a Samsung SyncMaster 192T.
It's not the latest model, but worked well as a second monitor. The monitor remains black, the green led on the front flashes. The system profiler states "no monitor connected"

I googled for the problem and it seems like there are quite some people with similar problems. Most of them being MacBook(Pro) users though. But there is no solution!?

I tried everything obvious: switched cabels, swapped cabels, installed latest updates, just connected this monitor as main monitor, restart. No luck.

I tried the monitor on my MacBook (no snow leopard) with the mini-display adapter: works. Then I found my VGA-DVI adapter and connected to the VGA input on the monitor: that works - doesn't look pretty though. so the problem is only the DVI connection to the MacPro with Snow Leopard.

Any ideas to solve this?

Thanks and Best
Kai