I had the same problem which I solved by what, charitably, must be called a work around.

Before you go through the same hassle I did, however, check to make sure that the little phone icons next to the name are not grayed out. If they are the contacts won't go. Apparently there is no universal or en masse way to activate these. You have to go into each record, check the "on phone" box and save. There are various mysterious nuances that will prevent you from doing this, like having the default phone number a fax, no phone number and others.

Also if you have over 600 contacts the phone won't handle it and other mysterious things seem to happen to the on line data base with the end result being they won't sync. In my case the helpful Sprint rep transferred my contacts from my Palm which totally screwed me up because fields were wrong, and then I had way too many contacts when I tried to Sync.

As a result of my frustration I think I am going to take the Instinct back, but here is what finally worked:

First you need to start with a clean slate. To do this I had to deactivate, then reactivate the mobile sync. (Selecting all the check boxes then deleting didn't work) Also delete contacts on your phone if having them will put you over 600.

On the Sprint sync site you will find an option to export and import. On import it guides you though a method to upload a .csv file from your computer. To get such a file you have to go into Outlook Contacts, pick 'Import and export' from the File pull down menu. pick 'export to a file' then 'comma separeted values'. Once it is exported and saved open up the new file in Xcel then add header lines that match those described on the import instructions on the sprint site. Save as a CSV file and then import it into the sprint web site.

If the little phone icons are not greyed it should sync after a while, but don't try to use your phone for some hours because that will just upset its overloaded brain and it probably won't work. You will still probably have to fiddle with fields to get it to work.

Maybe the better solution is just to return it and get an iPhone or Blackberry. When I went back to Sprint (after I had already purchsed the Instinct) the rep told me the Instinct was "really just a fun phone."