Incorrect value (null) deserialized. Make sure you are using CacheStorage inside single-instance application deployment only.

[Steven]

This started happening this afternoon in our production environment and we have not changed any code prior.  Everything was working fine.  It is unclear searching the forums and Internet what is causing and how to fix.  We are completely down.

[Todor]

Hi Steven,

I noticed that you have opened the issue also as a Support Ticket. I will copy my reply also in this forum thread, so that other users may benefit from it if they hit the same issue:

Please, check the KB article An AddInSet NullReferenceException Is Thrown on Requesting Reports which elaborates on the problem related to the error message and suggests workarounds.

If you use the default FileStorage for your Reporting REST Service, you may safely delete it and restart your Reporting application. The reason is that It may be corrupted and you should manually delete all expired assets.

I suggest also the blog post Telerik Reporting REST Service Storage Revealed for more details on what is the service storage and how you may solve problems related to this storage.

Regards,
Todor
Progress Telerik