I figured it out! My husband had a Palm Treo prior to the Moment. When I exported his contacts from the palm and imported them into Gmail contacts, the "labels" (work, home, mobile) came over but as "custom" fields (though they showed up in contacts as actual named fields) so Gmail was not recognizing them as proper labels! The Gmail labels are the same but still, different. The only way I was able to tell the differance was that the Gmail labels have the first letter capitalized! I was so frustrated with the problem that I downloaded handcent (I was resisting because my husband does not have much patience for new programs he can't figure out right away) and when I initially downloaded it, all of the contacts showed up. When I chaged the settings, however to show only mobile numbers when texting, I was left with only about 4 contacts. It took me awhile, but I figured out the problem! Thanks, everyone, for your help!
ps. you are probably right about formating, however, I was entering text recipeants by name, not number, so the number format wasn't an issue. Typing the name should automatically bring up the numbers/options.