How many request rows are affected? Is this the only row that throws an exception or there are many?
I would suggest to try to open Certification Authority MMC snap-in and try to retrieve the certificate from GUI. If GUI will continue to throw errors, then it may be caused due to CA database corruption.
I would suggest to try to open Certification Authority MMC snap-in and try to retrieve the certificate from GUI. If GUI will continue to throw errors, then it may be caused due to CA database corruption.