What does this mean?

[Ricardo Manuel Oliveira]

 Hi everyone.

 Today I started receiving these messages in bind's logs:

04-Dec-2000 04:02:40.639 response-checks: Malformed response
from [xxx.xxx.xxx.xxx].53 (query section mismatch
(xxx.xxx.xxx.xxx.in-addr.arpa IN PTR))
04-Dec-2000 04:02:41.242 response-checks: Malformed response
from [xxx.xxx.xxx.xxx].53 (query section mismatch
(xxx.xxx.xxx.xxx.in-addr.arpa IN PTR))

 What does this mean? (No, the xxx.xxx.xxx.xxx isn't one of
my machines).

 Best of regards, Ricardo.

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Ricardo Manuel Oliveira