zone transfers slow

[Nicole Skyrca]

Hello,
We have a master name server, and two slaves called icarus and lurch. 
Zone transfers to icarus
appear to be instantaneous (ie as soon as the master sends the notify).
There is either a 
short delay  (anywhere from a few minutes to 30 minutes) in the
transfers to lurch, or lurch
just doesn't transfer the zone at all.  According to the logs,
everytime a serial number is updated
for a zone on the master, icarus will trasfer the zone with the new
serial number, but lurch
may miss 5 or 6 serial number changes before it transfers a zone.  Does
anyone
have any ideas why this could be happening and how I could fix it? 
We'de like lurch to transfer
the updated zones as they get updated.

Some other information that might be helpful is that lurch is named the
SOA in all of our zone files.
Lurch also acts as a master to our secondary dns service provider.

Thank you in advance for your help. I'm fairly new to the DNS world and
I've been reading the
books and searching the admin list archives, but any additional help
would be greatly appreciated.

Thanks,
Nicole

Nicole Skyrca
Syracuse University
Computing and Media Services
Machinery Hall
315-443-5310
nskyrca at syr.edu