CRM 2013 Report Error: "An error has occurred. Try this action again..."

We were getting an odd error when running a CRM report in an environment that had been upgraded from CRM 2011 Online to CRM 2013 Online.

In short, we were getting the following rather unhelpful generic error message:

This error only occurred with a few of the records but ran fine for other records. In order to troubleshoot, I removed all the front end components of the report so that essentially the report would just have a blank rendering. And even after doing this, the report still gave up the error above.

So this seemed to point to the fact that there was some issue with the data set...

As it happened this data set had a link-entity join clause and I discovered that when you added in the linked record such that the join would succeed the report would run fine. And in cases where the join did not bring back results the report error would occur - this being our particular case.

So this explained why it occurred only for certain records whereas not for other records in the system. However it does not explain why this error occurs in the first place. At the most I would expect the report to not render results when a join does not bring back results. After all in many cases it is perfectly valid to have a join that does not succeed. Even if there was an error caused by the lack of the join, I would expect to see this error manifesting itself in the returned report as is the case for example when running a report where the sub-report it is calling does not exist.

All in all, while I'm glad I discovered the issue, this does seem very much like a bug in the platform to me.