Offcourse after searching Microsoft Connect (which I should have done in the first place) I found a bug report for SQL Server 2008:

https://connect.microsoft.com/SQLServer/feedback/details/554026/ssms-restricts-the-size-of-a-data-file-to-2tb

It should have been fixed in...

Allright I just fixed the problem.

There seems to be somekind of bug in the Database Properties GUI when you want to increase the initial size above 2TB.

When I increased the...

Unrestricted growth.

The database is on a SAN disk but the storage admins tell me there is no file size limit.

It is the database data file, so the MDF.

Some extra information I just found out:

Whatever I try to do the file simply won't grow past 2,097,152MB which happens to be 2TB exactly.

Does anyone know of a possible limitation...

You should keep an eye on the fragmentation of the index every day.

If you notice the fragmentation growing to high ( > 30% ) you should consider rebuilding the index...