sequence skips 30 values, how?

We are trying to track down an issue with our PostgreSQL application.
We are running PostgreSQL 7.4.13 on Red Hat Enterprise ES 3.

We have a situation where the postgres backend process drops core and
dies.  We've tracked this to an unusual situation where a sequence value
that is being created during the process that is causing the core file
generation.  The thing that is bizarre is that the sequence value skips
30+ entries.

How is this even possible?  Any suggestions would be greatly appreciated.

--
Until later, Geoffrey

Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety.
  - Benjamin Franklin