I logged this yesterday and have just received the following:

This case has just been escalated to me.

The issue you mention has been acknowledged as a bug, and a number of clients have encountered this error during testing and usage.

A patch request for this issue has been filed yesterday for Blackboard Learn 9.1 April 2014 release, otherwise this issue is scheduled for rectification  in the October 2014 release of Blackboard Learn, would you like me to add you to the patch?

As Product Development will be responsible for delivering the patch, we are currently unable to give an estimated availability date until they are able to provide us with further information, however this patch is being addressed as a priority .

Regards

Bob Foster
Client Support Engineer
Blackboard International

So hopefully a patch will be available before October – and it does also mean that upgrading to Oct 14 (impossible for us to contemplate) will not be the only solution.

best wishes