Problem upgrading to MySQL5 in Ubuntu upgrade to Lucid Lynx

Oh, something seriously wrong happened in the way to upgrading an Ubuntu server installation from Hardy to Lucid. The former PHP applications which I consider robust have all problems with the MySQL daabase! Our big Wordpress blog Digital Exploration is down due to

Error in Establishing a Database Connection!

which is kind of silly since all our previous MySQL database connections were working properly.

We hope that we will soon be back. All I can think of is to reinstall MySQL and Wordpress, in that order. As far as I can see, the MySQL server can run. It is the MySQL clients that cannot connect!

The problem was a misconfiguration, basically, the my.cnf file, involving copying the default config file to /etc/mysql/my.cnf I will expound further on this when we have the time.

Thanks to our VPS support team for fixing the error.