pix error message

Dear all,

i keep recieveing the following error message from my cisco pix
firewall.

PIX-3-305005: No translation group found for udp src
inside:192.168.0.63/138 dst outside:192.168.255.255/138 Jul 15 06:28:16
intpix Jul 15 2006 07:14:56: %

PIX-3-305005: No translation group found for udp src
inside:192.168.0.63/137 dst outside:192.168.255.255/137 Jul 15 06:28:17
intpix Jul 15 2006 07:14:57: %

note that i dont have inside ip address 192.168.0.63 or any address in
this range.

i suspecte that its kind of virus!

any help ??

thanx a lot.

.