IO slowdown with latest FC4 kernel

[Pedro Fernandes Macedo <webmaster margo bijoux nom br>]

Hello guys. I think I've stumbled across something weird.
My brother updated his machine today and since then he started to have 
horrible IO performance with kernel-2.6.13-1.1526_FC4. For example, 
transfering his stuff to my computer as a backup (we started to suspect 
the HDDs were going to stop working), the max speed with latest kernel 
was below 1MB/s. With  2.6.12-1.1456_FC4, transfer speed is over 3MB/s 
according to the ssh client I'm using right now.
Not to mention the average responsiveness of the system (a ssh login 
with 1526 took about 10-20 seconds to show the login prompt, while with 
1456 the prompt shows up immediately.

Any ideas on how I can test this to confirm if this is a bug or just 
faulty hardware? I'm going to run a full smart test on the discs 
tomorrow and a few RAM checks just in case, but the short test from 
smart passed without any problems and the smart reports shows no 
parameter outside the limits.

Thanks.
Pedro Macedo