BIND 8.2.3 and serial 0/slave server question

[David R. Kirk]

Does the old trick, that worked up at least up through BIND 8.1.2, of 
setting the zone serial number to 0 ("zero") to force a pull from slave
servers still work?  

We are providing slave service for a number of our customers, and we 
have always told them to set the serial number to 0 ("zero") when they 
mucked up their zone files and needed to bring sanity back to their 
zones before we could slave the zones.  However, of late, it seems that
this function is not working, or possibly not working in the same way
it once did.  Has anyone else seen this?  Am I totally off-base?  Am I
not waiting long enough for the slave servers to pick up the zones 
(though I have waited ~6 hours for one of the zones to be slaved)?

Any assistance/insight that anyone can offer would be greatly appreciated.