Slow droping tables

It would seem that my postgresql database system is getting slower and
slower at dropping tables and possibly other tasks too.

Am I being paranoid? I don't think so.

Can anyone think of anything that would cause dropping a table with little
data contained within it to take several seconds (and growing)? I have
vacuumed the database.

Here is a list of guessed on the factors which may be involved:
- there are several short/simpler triggers calling tcl functions on each table.
- upgraded to 7.1 but not to 7.1.2
- there is very little data in any of the tables - the project is still
under development and isn't getting any traffic
- we use scripts which create tables and while testing we've created and
dropped a lot of tables
- dropping a small table with little or nothing in it results in seconds of
hard drive churning.

Thanks for any feedback.

Andy Koch.