SQL Express Errors: Diagram Component, Startup Error

Problem 1: Upon starting SQL Server Express I get the following error:

"An unhandled exception has occurred in a component in your application....Cannot create a stable subkey under a volatile parent." Clicking OK lets the Server continue and I can use it quasi-normally.

Problem 2: Also, when I try to generate a diagram, I get a message that states

"Database diagram support objects cannot be installed because this database does not have a valid owner.  To continue, first use the Files page of the Database Properties dialog box or the ALTER AUTHORIZATION statement to set the database owner to a valid login, then add the database diagram support objects."

But, the database HAS an owner, and resetting the owner (using the Files...) to other users has no effect.

Problem 3: I tried to change the name of a database, and it refused to do so. Except that now all objects under the database name (it is the same old name) have disappeared. Is there a magic folder somewhere that contains all of the tables, etc. that were 'banished' from the server?

Is there a way to detach the databases from Express and reattach them to the SQL Server 2000 I am also running? Last time I tried the 'detach' worked but all the objects were wiped out by the 'attach'. Handy feature.

Thanks

Glen