Radeon X1900 XT in MacPro problem with Samsung monitor

CPU = MacPro dual core Xeon 3 GHz. Bought used, works fine. Bought Samsung 2430HD with 1920 x 1080 resolution to run as main monitor. AMD Radeon =
Chipset Model: ATY,RadeonX1900
Type: GPU
Bus: PCIe
Slot: Slot-1
PCIe Lane Width: x16
VRAM (Total): 512 MB
Vendor: ATI (0x1002)
Device ID: 0x7249
Revision ID: 0x0000
ROM Revision: 113-A52027-202
EFI Driver Version: 01.00.202

Problem: The Samsung does not handle the signal from the ATI properly; it displays all 1920 x 1080, but it compresses the left side of the screen by about an inch and a half. So, aside from wasting 10% of my screen territory, all circles/images/everything are a bit vertically ovoid/compressed. Video works OK. Sure would be nice if it worked properly...

I'm using an older Acer FP563 (1024 x 768) as a second monitor. Symptoms are not corrected by switching monitor plugs on card. Or by removing Acer.

Samsung displays properly on my MacBook. I've repaired permissions, reset PRAM, tried booting off another hard drive. Still leaves left side blank. If I go down to lower resolution, it fills screen (but looks crappy). Samsung support was not helpful.

Does the Samsung monitor have an auto adjust button? Try that. Also what refresh rate are you running at? For the LCDs should be 60.

The screen adjustment is out of the picture, usually. I've seen it on LCDs but it's been on pretty pricy monitors. The auto adjust button has always worked for me to shift an image back in to position. Another thing you may try, do a factory reset on the monitor, should be an option in the on screen controls.