Strange IPv6 related DNS lookups

Hi,

When connecting via ssh from a 1.5.3 machine to a 1.6 machine
(both IPv6 enabled), I get the following DNS lookups:

22:17:32.454038 192.168.2.2.65352 > 192.168.2.5.53:  43353+ AAAA? 
fec0.steinba.ch. (33)
22:17:32.454327 192.168.2.5.53 > 192.168.2.2.65352:  43353 NXDomain* 0/1/0 
(81)
22:17:32.455635 192.168.2.2.65351 > 192.168.2.5.53:  43354+ A? 
fec0.steinba.ch. (33)
22:17:32.455756 192.168.2.5.53 > 192.168.2.2.65351:  43354 NXDomain* 0/1/0 
(81)
22:17:32.456885 192.168.2.2.65350 > 192.168.2.5.53:  43355+ AAAA? fec0. (22)
22:17:32.457035 192.168.2.5.53 > 192.168.2.2.65350:  43355 NXDomain 0/1/0 (97)
22:17:32.458142 192.168.2.2.65349 > 192.168.2.5.53:  43356+ A? fec0. (22)
22:17:32.458253 192.168.2.5.53 > 192.168.2.2.65349:  43356 NXDomain 0/1/0 (97)

The 1.5.3 machine's interface has the following addresses:
192.168.2.5
fec0::200:1cff:fed3:c313 prefixlen 64

The 1.6 machine's interface has the following addresses:
192.168.2.2
fec0::200:83ff:feae:2193

The 1.5.3 machine is running the name server.
On the 1.6 machine, /etc/resolv.conf looks like this:
nameserver 192.168.2.5
search steinba.ch

What's going wrong here?

Kind regards
    Ingolf