Hello Friends, thanks for sharing the info on this. This is very helpfull. I got the same issue today and did multiple things......

1. the database is msdb, which caused the issue.

2. I figured out the issue is with Full Text files associated to my userdb's and I am having access denied issues even though my service account have full access to the file locations.

3. restart sql server did not work for me. I was able to rename the msdb physical files ever after sql restart. which means msdb is not connected to sql.

4. FINALLY, I rebooted server and then it worked..... :)..... and I think its the file permission issues.... and am assuming permissions were refreshed and am able to connect.

gud luck with this... this is a serious problem if its on prod. Make sure you have the backups available as a last option.