Problem with 7.4.1 and complicated queries

Cheers,

I have a problem with postgresql7.4.1 on a SuSE machine. I use the
database for a C#-application for a small company to store their
clients, sales, etc... This all works flawless since 1 year. Since 2
weeks the database hangs if I perform long queries with views involved
in order to generate long reports about sales per month per categorie
and so on. The database does not respond and only I dump the database
and work on the dump I can continue. Working on the old set does not
work.

Each night, I run vacuumdb, but it does not help.

Is this something known?

I can send you more information if needed.

Thanks,
Jonathan