Excel (and all windows programs???), use a combination of the printer driver and
the display driver to determine what to show on the screen.  (In fact, you may
find that sometimes the cells look nice on the screen, but print ####'s.)

You can make the columns as wide as you think they need to be (plus a touch
more) to see if that helps.  

Or maybe you could play with the font.
format|cells|alignment tab|check Shrink to fit
(in the Text Control section)

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Another problem can be dates.  If you use mdy (like mm/dd/yy) and I use
mm/dd/yyyy then I'll need the columns to be a bit wider--or I'll see those
######'s.

It sometimes helps to use print 1 page wide and 1 page tall.
Or, for some clients I have had to actually load their printer driver on my
computer for testing in print preview mode.