Why does MS Excel freeze and get forced to close every time i try to format any cell or cells?

In microsoft excel if i right click and hit Format Cells, try to use the quick buttons to change cell alignment, or even go to the Format drop down and click cells, the entire program stops working. This hasn't always been the case, but has just recently started to happen. I cannot figure out why and its getting very annoying. I should also say I have even uninstalled, and re-installed the entire set of MS office programs. Anyone have any idea why this is happening?

I am running Windows Vista Home Basic on a Dell Inspiron 1501. The program is MS Excel 2003.