Can't start / stop MySQl (1 reply)

I am having problems startig stopping MySQL without rebooting.

- I have had to reinstall MySQL recently
- I could recover the database from a backup
- However I am having several problems

1) mysqld stop
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111028 16:37:19 [Note] Plugin 'FEDERATED' is disabled.
mysqld: Can't find file: './mysql/plugin.frm' (errno: 13)
111028 16:37:19 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
111028 16:37:19 InnoDB: Operating system error number 13 in a file operation.
InnoDB: The error means mysqld does not have the access rights to
InnoDB: the directory.
InnoDB: File name ./ibdata1
InnoDB: File operation call: 'open'.
InnoDB: Cannot continue operation.
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First question; which library is this (in the GUI)? I may have managed to change this during reinstallation?!