I've tested this on my SQL 2005 server and can't get it to save an object in System Stored procs.

Are you sure they are actually defined as system stored procs? In SQL 2005 the view is a bit misleading as there isn't a seperate User Stored Procs folder. All the user stored procs appear under "Stored Procedures", and there is a seperate "System Stored Procedures" folder on the same level, but it's at the top of the list, so it does look a bit like everythin is in that folder.

Cheers

Leo