Hi Nick,
I ran into this with a customer recently and we found in their infrastructure there was a separate reporting database that only replicated from Prod every few hours. This produced a situation where blank reports would show if the report pointed to an Incident or other such record that had not yet replicated from the Prod DB to the reporting DB.
I actually think this might have been a case with you, but I figured I should note something here in case you are a different Nick or others see this in the future.
Jon