My guess is that your certificate issuer is wrong and that the error is due to the length of the Certificate Name.
I struggled with exactly the same symptom on the weekend before finding the following KB Article:
http://support.microsoft.com/kb/2496441
The (Fully Qualified) Certificate Name cannot exceed 128 characters, as the 'Name' column in the 'Certificates' table in the Deployment Database (MSCRM_CONFIG) is defined as NVARCHAR(128).
Unfortunately for you, me and anyone who picked the wrong certificate issuer, our Certificates are incompatible with the Claims-based Authentication configuration process as it currently stands.
I created a Change Request in Microsoft Connect because a) it would be easy to fix (ALTER TABLE ... ALTER COLUMN) and b) it is going to affect anyone attempting to configure Claims-based authentication and happens to be unlucky enough to pick the wrong certificate
issuer (something you aren't going to know before starting this process).
--pogo (pat) @
pogo69.wordpress.com