Two images side by side is 31kHz on a 15kHz monitor. Three is 45kHz. It's not good for the monitor to leave it running that way, but it happens to all of us unexpectedly from time to time.
You've either set something wrong, or that card won't work with crt_emudriver. Plug in an LCD when you get the side by side images, and see what modes are listed in ArcadeOSD, mb. Make sure to consider hidden modes as well, because if you can't turn EDID emulation on, window will pull modes from the monitor's EDID.
The firepro cards can emulate an EDID with their normal drivers, IIRC, but they're not even legacy cards, i don't think they've ever been supported by crt_emudriver specifically. Sometimes you can get away with mobility versions of supported cards, or mb APU versions, but I reckon these are going to be too different.