Mysql ERROR?

Hi everyone,
sorry for my bad english, I’m Italian,
I’ve a little problem and I don’t know how to solve it.
I’m under Ubuntu 6.06 and I’m using rubyonrails.
Everything worked fine, but I changed something and now I’m getting this

Mysql::Error: Lost connection to MySQL server during query: SELECT, t2.tag, COUNT( AS n FROM tags AS t1, (…)

What I did?
I UNinstall and install again mysql: it was my fault.

Thanks so much for any your reply!