Is Pg 7.0.x's Locking Mechanism BROKEN?

Hello;

we've been using Postgres for nearly 2 years now, and have
followed updgrades, from 6.4.2 to 7.0.2. Our applications
are mainly shell scripts, and CGI. All is done in perl.
We have long, heavy, and simultaneous transactions.

With 7.0.x versions, we've come across a problem, new for us:
very often (2 or 3 times a day), there are on our Pg machine
a dozen of 'update waiting', and our perl scripts are waiting
too to begin a transaction. So many postgres are running, than
no other one can be added; only SELECTs continue to be possible.
We finally have to restart Postgres; but even if we kill
postmaster's process, there still are postgres processes runnings,
and they have to be killed too! Definitely not working.

We've been looking for solutions for a few weeks, and even
decided to move Pg from a satured PIII 650 to a DEC Alpha 500mhz,
where Postgres is the only application to run.
So far, we haven't found any workaround, and the hangings have
been quite nasty for our project.

Yesterday, I moved back our DB to Pg 6.5.3, and yes, now
everything works fine again (it's slower, but it works).
And vacuums don't hang the postmaster any more.

So, I've got 2 questions:
- Am I the only one here to have such problems with 7.0.2?
- Is 7.0.2 broken?

Regards
Fabrice Scemama