This message does often occur when someone attempts a DCC exploit against you, although I think in your case this is unlikely.
If you're using DSL go to
ALT+O > Connect > Options > [Advanced] and input your LAN IP and check "Bind sockets to this address".
There have been a large number of threads about DCC resume and indeed this issue specifically. I suggest you run a
Search on 'DCC Resume' and expand to 'All Forums' and 'All Posts' for best results.
Best of luck.
Regards,