IP_MASQ:reverse ICMP: failed checksum from x.x.x.x!

[Peter Schnebel <debian@babylon-systems.de>]

hi there !!

i got the message "IP-MASQ:reverse ICMP: failed checksum from IP!" today on 
our router...
what does that mean ??

i tried to ping that ip and it was up... an nslookup brought nothing...
after running an nmap on our router i saw 2 extra ports open with curios 
names...
with the next nmap the 2 ports had disappeard ( that's why i can't tell the 
numbers )...

the only open port on the router is the "sunrpc"... we also got 
port-forwarding to our local web-server...

could it be that we got hacked ??

thanks in approach

peter