ATI 2600 artifacts during boot of Mac Pro

I'm wondering if anyone else has experienced this so I can write it off as "normal" and move on.

Refurb 2.8 8-core, stock configuration + Airport Extreme card
Display one: Samsung 204T via DVI
Display two: AG neovo M-15 via Apple DVI-VGA adapter

During start-up, some artifacts appear on the upper left corner of my Samsung display...basically rows of lines, maybe 4 inches of them vertically that stretch about 2-3 inches horizontally each (like a multi-pronged fork or hair pick through wet sand for a mental image). Upon boot, only the Samsung is running, then the artifacts happen for a second or two, then the display goes dark and then both displays come up without further incident. Haven't noticed any problems during regular use, which has been 4 days worth.

Didn't have this sort of thing on my Sawtooth G4 using the same displays hooked up to a flashed ATI 9200 AGP, so I feel safe in saying it isn't the displays or cables...and both cables are securely connected. Also, with the G4 the displays both came on together and didn't go dark/come on again.

Thoughts, comments and observations appreciated!