Because, there is a bug in the implementation, or someone did not think of this problem.
The login procedure could try kerberos at the first attempt, but then must fall back to ntlm - which it doesnt.
The only way to use kerberos for login to a remote domain is to establish a trusted relationship between the two domains - this is an unlikely setup to expect.
Maybe this is even a kind of security feature, which simply does not allow you to login to your PC at home, because you then could copy secret information from your office to an unknown/untrusted PC.
I tried to find information about the files feature on RIMs site, but found only this:
JAAS Login Configuration File
referencing the mdslogin.conf
And the file looks ok.
But even if this looks ok, nobody seems to know if the files features uses the mdslogin.conf at all.
anyone else with a good Idea ?