why this error?

[gt1cjh at gmail.com (zhaoj)]

[*] Calculating the number of spoofed replies to send per query...
[-] Auxiliary failed: Resolv::DNS::DecodeError non-backward name pointer
[-] Call stack:
[-]   /usr/lib/ruby/1.8/resolv.rb:1375:in `get_labels'
[-]   /usr/lib/ruby/1.8/resolv.rb:1379:in `get_labels'
[-]   /usr/lib/ruby/1.8/resolv.rb:1361:in `get_name'
[-]   /usr/lib/ruby/1.8/resolv.rb:1525:in `decode_rdata'
[-]   /usr/lib/ruby/1.8/resolv.rb:1403:in `get_rr'
[-]   /usr/lib/ruby/1.8/resolv.rb:1308:in `get_length16'
[-]   /usr/lib/ruby/1.8/resolv.rb:1403:in `get_rr'
[-]   /usr/lib/ruby/1.8/resolv.rb:1285:in `decode'
[-]   /usr/lib/ruby/1.8/resolv.rb:1284:in `each'
[-]   /usr/lib/ruby/1.8/resolv.rb:1284:in `decode'
[-]   /usr/lib/ruby/1.8/resolv.rb:1301:in `initialize'
[-]   /usr/lib/ruby/1.8/resolv.rb:1265:in `new'
[-]   /usr/lib/ruby/1.8/resolv.rb:1265:in `decode'
[-]   (eval):424:in `calculate_race'
[-]   (eval):264:in `run'
[*] Auxiliary module execution completed



uname -a
Linux stt 2.6.24.4-64.fc8 #1 SMP Sat Mar 29 09:15:49 EDT 2008 x86_64
x86_64 x86_64 GNU/Linux

Why ? anybody can tell me ?