SYMPTOMS
When you try to use the DNS snap-in in Microsoft Windows Server 2003 to delete DNS PTR (reverse lookup) records that contain uppercase characters, the operation may not work as expected.
CAUSE
http://support.microsoft.com/kb/842127/en-us
SOLUTION
Delete PTR manually with the Microsoft "DNSCMD.EXE" tool available in ressource kit. In the Microsft KB the KB suggest you to remove all PTR in reverse lookup zone "oh my god".
This is the solution to delete only one PTR in DNS Reverse Lookup zone.
Sample to delete the PTR number 34 and 35 :
dnscmd /RecordDelete 10.192.168.in-addr.arpa 34 PTR
dnscmd /RecordDelete 10.192.168.in-addr.arpa 35 PTR