Excel 2011 unusably slow even on i7?

Hi folks,

I run a spreadsheet for processing expenses and so on for my small business. It's not huge but not trivial by any means. However, though I'm running it on a 2.9GHz i7 quad with plenty of ram and an SSD disk, it still runs almost unusably slowly. Oftentimes there are pauses of up to a second when I'm moving between cells.

Anyone know what's going on? I am fairly positive that it's not meant to be this slow, but successive software updates haven't changed things so I'm beginning to wonder. I'd port it into a different app (Numbers?) but I'm not convinced that doing that would be an easy process as there are a lot of summations and some conditional logic behind many of the cells.

I'd understand it being slow on (say) an old creaky machine, but a quad core i7? Surely not.

Anyone?