Although it is said to be fixed, I still encounter crashes on the blacklist db. Deleting the blacklist db file and restarting sshguard service helps for a certain amount of time. Can't say for how long. At first it crashed at 18 lines in the blacklist file. Today I discovered it had crashed again with 78 lines in the db. And agian, deleting the blacklist file and restarting the service helped.
My system is FreeBSD 10.1-RELEASE-p16 SSHGuard installed from binary package, version 1.6.1, IPFW
On another FreeBSD system (10.2-RELEASE) and same version of SSHGuard, the service crashed with 25 lines in the blacklist db. Same story here. Deleting the db file and restarting worked (until the next crash)
I also noticed that the IPFW blocking rules for all those IP addresses in the blacklist db where gone. I assume these have been removed while the service was running.