To get started I ported a small test program to S60 Rel 3 and always got a User 11 Panic during startup of the program. This was very strange because at this point even the document class wasn't instantiated and my program didn't have a chance yet to do anything wrong.
I found that the problam was caused by a UID I used for my testprogram. This program doesn't do much and so I used a UID from the 'Unprotected Range' I got from the Symbian Signed webpage. After I changed the UID to a UID from the 'Protected Range' and my program just runs as expected.