Bossel,

This could be caused by only a couple of reasons.

One: this could be the result of a backward compatibility issue. What version of Excel are you using?

Two: Is your excel spread sheet saved as a .CSV?

Three: Are you able to export your current contact list to a .CSV to be opened into an excel sheet so you can compare formating?

Here is a Microsoft article with some additional info; http://support.microsoft.com/kb/295664

Keep us posted