[Koha] new install: z3950 client not connecting to servers

Just installed Koha on Debian Sarge (testing). Used the 2.0.1 tarball from sourceforge. Looks good, except that searching for isbn or title using z3950 returns "server not responding" for all my biblio servers. I've checked my installation against all the docs I could find, searched the mail list, and I'm just not seeing the problem. Not sure what other information you need. Can someone help?