Hi Black.Jack,
are you testing against the Alfresco-CMIS cloud?
I tried the same, but cannot reproduce your exception.
The only special case I know with Alfresco is that you get two objects in folder if you check-out one, and only the one with (Working-Copy) can be checked-in.
The exception you get is a request to identify Alfresco-Aspects properties (CMIS does not have an API to get them), I know that on some Linux systems the Basic-Authentication header was not created correctly.
Can you provide some environment information?
My tests where done from an Windows 7 environment, tomcat 6.0.33 and JDK 1.6.0_33.
Cheers,
D.evil