SBS2003 - can't delete reserved IP

When I try to delete reserved IP it seems like everthing is OK, but when I
make refresh reservation is back. :-(

The same thing happens in cmd prompt ... here is copy ...

netsh dhcp server scope>delete reservedip 192.168.133.22 00-03-1b-58-c8-aa-
Command completed successfully.

netsh dhcp server scope>show reservedip
================================================== =============
Reservation Address - Unique ID
================================================== =============
192.168.133.25 - 00-00-85-80-47-1e-
192.168.133.26 - 00-80-87-4b-9e-ab-
192.168.133.22 - 00-03-1b-58-c8-aa-
192.168.133.28 - 00-00-85-80-46-c4-
No of ReservedIPs : 4 in the Scope : 192.168.133.0.
Command completed successfully.
netsh dhcp server scope>