I have been using an SMF forum for almost 5 years (
www.todopic.com.ar/foros). We have had some serious problems with the database, problems that have collapsed the forum for hours.
The problem with some web hosting services is that they use one server for several web sites and services (php, html, asp.net, etc.). When other websites receive lots of petitions, the smaller websites (such as eevblog forums) are affected aswell.
The database error is most likely occasionated by the server cpu load.
We had to move to a faster web hosting company.