Type / Dreamhost & strange mysql timeout


I have a Typo blog hosted on DreamHost (Version 4.0.3 /
www.pierocampanelli.info). It worked nicely for months without any
concern. I stopped writing new posts for 2/3 months. Yesterday I tried
to publish a new post but it miserabily failed.

When I try to do any “transaction” (write article, delete cache,…)
page stalls till a Typo Rails Error appears.

Searching in the log I found this entry:

ActiveRecord::StatementInvalid (Mysql::Error: Lock wait timeout
exceeded; try restarting transaction: DELETE FROM
WHERE id = 30

I tried to kill all and restart rails but also this morning the
problem continues to show.

What happened? Have you any clue to follow?

Thank you