You need to setup your IRC client so you can debug the incoming CTCP request that initiates the DCC send. This sounds like a router issue, where the router can't perform loopback requests on your external IP. There is nothign you can do to fix this, without breaking DCC sends for other users. Besaid...
The only real method is to pass a second argument with the length of the data.
This pretty much goes along the lines of putdccraw. You can pass and use embeded NULLs in the data. For it to function correctly, the length is passed.
This means you have compiled your bot with the debug flag. When it dies, it creates this core file. The idea being that you can find out exacly what cuased it to crash by following which part of the code killed it. Your best bet is to delete this file, then recompile your eggdrop, though not from CV...