Synchronization problem

[Steffen Steck]

Next problem i have:
This morning my secondary dns on winnt4sp5 logged serveral 6527 errors
(saying that zones are no more available...). Now i want to synchronize
my secondary dns with my primary (on HP-UX) manually and get an error
6525 (the same was logged before the 6527 event...) saying :
Zone transfer request for secondary zone domain.de refused by master DNS

server at ipadress.
Has anybody any ideas?
Everything worked fine the whole time till 9 am this
morning. Permissions on the UX machine are also fine, the DNS on this
machine also.
Thanx in advance