Are there perhaps any APs around whose SSIDs have a '/' in them or
aren't UTF-8 safe? There was a bug in NM versions before 0.6.6 which
could cause crashes in certain circumstances. This could happen when NM
would try to push the network object paths back through D-Bus in reply
to your getNetworks() call. I'd give 0.6.6 a shot because that would
most likely fix your issue.
Dan