Slow DROPing Table

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 triggers on each table.
- the table does have a referential constraint ON DELETE CASCADE
- 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, we CREATE and DROP a lot of tables

Thanks for any feedback.

Andy Koch.