I have v 1.0 of this library and I'm using arduino v 1.5.
There's a problem with DNS lookups which seems to manifest itself when looking up local hostnames.
I think the problem is in inet_aton which is supposed to convert a string IP address to IPAddress type.
To find out it tests each character in the string for numerals:
while (*p &&
( (*p == '.') || (*p >= '0') || (*p <= '9') ))
but any alphabetic character matches *p >= '0'
It should be:
while (*p &&
( (*p == '.') || ((*p >= '0') && (*p <= '9')) ))
This may have been fixed in later releases but the change long doesn't mention it.