Actually there was a hotfix for this that came out after Service Pack 1 came
out. You can refer to kb899341 that says that this fix was supposed to be
included in Service Pack2.
Description of the Project 2003 post-Service Pack 2 hotfix package:
February 28, 2006
(899341) - File name File version File size Date Time
Office2003-kb899341-glb.exe ...
http://support.microsoft.com/kb/899341/en-us
In the section that says List of Issues Fixed you will see "When you try to
connect to Project Server 2003 by using Project Professional 2003, the logon
page is blank." I heard this hotfix never actually made it into service pack
2. I had applied it after Service Pack 1 came out and it resolved the issue.
As soon as I installed SP2 it started happening again, and trying to reload
the old hotfix "Project 2003-KB899341-Fullfile" no longer works after SP2 is
applied. Anyway its a known bug.