Make sure the resolution you're trying isn't below 256x256. Any number below that will instantly crash (and be completely unreadable and probably unplayable anyways).
If you set it from the configuration graphic interface it can have that problem, try setting it from the GSdx.ini (open with notepad) file in the PCSX2\inis folder, it's the resx/resy lines.
Core i5 3570k -- Geforce GTX 670 -- Windows 7 x64
Why would you play it at lower resolutions than the original PS2 can offer? It's just eye cancer. Just play it in your PS2.
Yeah, have to admit, after experiencing PS2 in high resolutions, I'd consider even native to be quite distasteful.