Severe performance issues

[Limaunion]

Hi,

I've been running Ubuntu at home since the first days, switched from 
Fedora in my two computers. Today I installed Hoary at work in a new 
computer (one of the latest HP models) and updated it with the latest 
packages via apt, I wanted to give it a try.

Ubuntu was installed booting with the 'server' parameter (minimal 
packages) in order to run Postfix as a relay server. After just 10 or 15 
minutes the server had all of its RAM exausted (256MB) including virtual 
swap space (750MB). The OOM started to work and froze the system. 
Exactly the same service and configuration was previously running in a 
P1 166Mhz with 128MB of RAM with RH 7.3 without any problem for the last 
3 years (now is having some hard disk issues, so the change). I solved 
this by just picking another computer and installing RH 7.3 again.

I know this is not the right way to report a bug or a kernel trouble, 
but just want to say that something is very wrong with the default 
Ubuntu kernel, any ideas.

Regards,
Limaunion.