Recently I came across couple of services with a similar problem. May be this is how they restrict it. I'm really interested to know, why WSDL access is restricted this way. But you can download the WSDL and run the import and it works fine..
Thanks & Regards, Ravi C.Kota
SCJP 5.0, OCDJWS 5.0
Just tried the exact wsimport command in OS X 10.6.5 and there were no problems whatsoever. Client artifacts were produced and compiled.
I do suspect that this is of little comfort or use to you.
Which OS are you using?