BUG #5491: Queries performing slowly

The following bug has been logged online:

Bug reference: 5491
Logged by: Piergiorgio Buongiovanni
Email address: piergiorgio.buongiovanni@netspa.it
PostgreSQL version: 8.4.3
Operating system: x86_64-redhat-linux-gnu
Description: Queries performing slowly
Details:

Hereby our production environment:

PostgreSQL 8.4.3 on x86_64-redhat-linux-gnu, compiled by GCC gcc (GCC) 4.1.2
20080704 (Red Hat 4.1.2-46), 64-bit

The problem we have is simply queries perform very slowly. I simply ask the
DB SELECT * FROM business.Subject and the response time is 640555ms for 86
rows extracted. It's unbelievable!
Do I have any way to analyze the problem and the possibility to see anything
in the log?
At the moment I am not able to understand the problem as the database was
built following best practices.
This is our Enterprise Information portal database and we must understand
what is the problem.

Could you suggest me something to do?

Thank yo uin advance

Regards