impossible log message

I see occasionally copies of the following line in my email server's log. I looked at the kernel source and found point where this message is output. But, that portion of the code is marked as an 'impossible' case by comment. Obviously, that's not true. My question is whether this message has any security or stability consequences. I never had any problems with that server but, it would be good to hear if somebody has a more definitive answer. -- Mar 25 20:05:12 mail1 kernel: neigh_timer_handler(): timer & !nud_in_timer -- Selcuk PS: My server is a dual Xeon system running Suse 8.1.