bind9/dhcp3 DDNS error

Sun Mar 11 21:28:10 UTC 2007

Hello, i have small network (25 PC) with windows 2000/XP and debian 
server with dhcp3 and bind 9

While trying to implement ddns (dhcp updates dns), there is a problem 
with updates.
Clients are able to register in the reverse zone, but there are no
records in forward zone. In log, these lines are present:

hts-fw named[2100]: client 192.168.1.10#1175: updating zone 
'company.sk/IN': update unsuccessful: Brinza.company.sk/A: 'RRset exists 
(value dependent)' prerequisite not satisfied (NXRRSET)
Mar 11 21:56:53 hts-fw named[2100]: client 192.168.1.10#1178: update 
'company.sk/IN' denied

Have anyone idea what i'm doing wrong?