iMac Blender Grinds to a halt

I invested in and IMac a few months ago - and no problems until a few days ago. When I try to do arrays the programme grinds to a halt. I am running Lion 10.7.2 on 2.7 Ghz with 4 GB of memory. I am running the standard AMD Radeon Graphics Card, HD 6770 (512MB). I searched the Forum for solutions, but none of the basic suggestions made any difference. Apple support say that it’s not possible to adjust the graphics settings. Their only suggestion is that I load Windows 7 on the Mac, since Blender ran smoothly on that OS prior to me switching to the Mac. Can anyone tell me if this is a sensible solution or is the problem likely to persist?

When I try to do arrays the programme grinds to a halt.
A particular file ? Are other modifiers used

Can anyone tell me if this is a sensible solution or is the problem likely to persist?
Who knows without some further info (blend file ideally for example). Blender works fine on OSX from my experience