I am working on a computer with XAMPP installed on Windows 7. When I upgraded XAMPP to fix the earlier problem with WinMySQLAdmin, a new problem with mysql was introduced. The error log (mysql_error.log) showed the following entry at the end:
[ERROR] Fatal error: Can’t open and lock privilege tables: Incorrect key file for table ‘user’; try to repair it
To fix, I downgraded to earlier version of XAMPP, exported the database and removed the mysql data directory, and reinstalled the latest version of XAMPP. Now, MySQL could start without problems. Then, I imported the data back and all was well.