7.4.1 upgrade issues

I upgraded my main production db from 7.3.4 last night to 7.4.1.  I'm
running into an issue where a big query that may take 30-40 seconds to
reply is holding up all other backends from performing their queries.
Once the big query is finished, all the tiny ones fly through.  This is
seemingly ne behavior on the box, as with previous versions things would
slow down, but not wait for the cpu/resource hog queries to finish.  The
box is Slackware 8.1, on a fairly decent box with plenty of ram, cpu,
and disk speed.  I've considered renicing the processes, I was wondering
if anyone had a different suggestion.

TIA,
Gavin