You have a few choices.
Fill those blank cells (in the original data) with
1. a spacebar (yech).
2. an apostrophe
3. a formula that leaves the cell looking blank. =""
I like the third. I hope that it reminds me that it's there for a real reason.
Or fill them with something you like better.
A quick way to fill that range:
select the range
edit|goto|special|Blanks
type what you want and hit ctrl-enter to fill all the cells in the selection
