Have you gotten this solved yet?
I had the same problem, I came upon your post and it helped me to find the answer. I also had a "dash" in my hostname. I got rid of that, and it has since not added any unmatched entries to the cron portion of logwatch. I beleive there is probably a bug in the cronwatch scripts that something should be put in quotes somewhere, but the Logwatch scripts are very complicated, I took the easy way out and just got rid of the "dash" in my hostname.
I am using logwatch.pl,v 1.87