Archive Provider Support in SuperOffice 10.1

We use Archive Providers and since upgrading to 10.1.2.1565 these have stopped working even though we have re-compiled the code with the latest DLLs.

Whenever we try to use them, we see the following error (only if the provider contains data)

Looking at the request that fails, I can see that this is the problem:

Please could you advise how we can resolve this, if possible; or is this functionality no longer supported?

Cheers