Posrgres speed problem

Hi,

Im having a problem with postgres 8.1.3 on a Fedora Core 3 (kernel
2.6.9-1.667smp)

I have two similar servers, one in production and another for testing
purposes.
Databases are equal (with a difference of some hours)

In the testing server, an sql sentence takes arround 1 sec.
In production server (low server load) takes arround 50 secs, and uses
too much resources.

Explain analyze takes too much load, i had to cancel it!

Could it be a  it a bug?
Any ideas?

Thanks in advance