In order to be able to log on to Project Server 2010 with Project Professional 2010 you will have to create a profile in Project Professional.  Here is how:

1. Open Project Professional 2010 application. If prompted for a profile, select ‘computer’

2. Click on File, Info.

3. Click on Manage Accounts.

4. If your connection does not exist, click on Add.

5. Type in the Account name of your liking.

6. Type in your project server URL.

7. Click on OK.

8. You may want to check ‘Use my default account’ or ‘chose an account’ when starting.

9. Click OK.

10. Close Project Professional 2010.

11. Re-open Project Professional 2010 and select the desired profile.