Load problems...

Hi,
Does postgresql have any problems managing load? I'm running a medium sized
(30k customers) ISP off a postgresql database but it can't seem to manage
very well with the dozen or so requests per second it receives. The machine
we are handling is plenty powerful enough for a database like this (a dual
1ghz p3 machine with 1gb of ram) but for some reason it never runs quite
perfectly. 7.1.3 would overload the system rapidly and slow to a crawl, so we
installed 7.2b4 only to find it runs like a dream (less that 10% cpu usage
most of the time) but eventually fails to fork and crashes and burns, at
which point i have to restart it. Could anyone shed any light on a possible
solution to these problems?
Thanks,
    Daniel Andersen