dropdb - still occasional failures

We still seem to have occasional problems with dropdb while running 
contrib installcheck. The symptoms look like this:

============== dropping database "regression"         ==============
dropdb: database removal failed: ERROR:  database "regression" is being accessed by other users
============== creating database "regression"         ==============
createdb: database creation failed: ERROR:  database "regression" already exists
pg_regress: createdb failed



Example: (FBSD again) 
http://www.pgbuildfarm.org/cgi-bin/show_log.pl?nm=cockatoo&dt=2004-12-13%2008:10:01

I guess we could put a small sleep before dropdb in pg_regress.sh to 
make sure a backend from a previous client had enough time to clean up 
after itself, but I am wondering if this is a symptom of a larger problem?

cheers

andrew