Ok, I'll try to focus on client side. Now I've installed XP SP3 with IE8 and FF3.6 and there is the same problem.
"* Check that IE is configured to use Kerberos by reference." How to check it? In addition: When I start IE on XP machine, with Wireshark I get: KRB Error: KRB5KDC_ERR_C_PRINCIPAL_UNKNOWN R.
