Problem Selecting Members to add to new Distribution Lists

I have been creating and using Distribution lists for years. Using Outlook
2007/Vista. Problem started today when I created new Excel spreadsheets and
imported them into new Contact Folders. When I go to create a New
Distribution list and SELECT MEMBERS - none of the contacts are displaying.

I have already right clicked on the main CONTACTS FOLDER as well as the
individual contact folders below to make sure the "Show This Folder as an
Outlook Address Book" is checked. I am stuck and cannot find a solution
online.

Also, in the original Excel spreadsheets that I imported, I removed the
PRINT AREA and DEFINED THE NAME again for each folder. Then tried to import
the files again and create the distribution lists fresh. Still not working.

Please help! Thank you!