Cname problem with Win2kDDNS

[Colin]

     I've searched the archive and couldn't find anything close to the
behaviour we're seeing, so I'm hoping it's a simple config thing in Win2K we're
missing.  What's happening is that periodically, CNAMES inserted by Win2K
vanish for a period of time (1 to 12 hours) then magically reappear.  All of
the other DDNS records are not showing this behaviour.
     The version of BIND is 8.2.2 (please don't say upgrade, that's not an
option at this time), and it seems to be at least somewhat dependant on load. 
We've also noticed that it's more likely to happen when several DDNS updates
for CNAMES occur in a very short period of time.
     If someone can point me in the right direction it would be greatly
appreciated.  Also, I'm quite willing to provide more information if that will
help track this down.  I'm just not sure what other information might be useful
in this case.  I appreciate the assistance.

Cheers,
Colin