There have been several reports about problems with the use of navicat and/or mysql along with the use of a repack with integrated sql system.
The reason why a problem pops up in navicat when trying to connect to the database, saying the following sentence:
"Access denied for user 1106" or something
may be due to the password username given by you to the database.
Some repacks have specified username/password and that's the one you'll have to use when trying to access the database via navicat, sqlyog and so on.
A problem derived by this may also occur in the mysql installation, rendering the service unable to run properly.