Why are attachment(s) in a Test Case (under the Test Plan module) NOT showing up on the Test Case under Test Lab?

We use HP-ALM 11.00 Enterprise Edition - we have Test Cases under the Test Plan module with attachments, but when these Test Cases are pulled into a Test Set under Test Lab, the attachments on the Test Cases are not being brought over.

Is this an with some Settings? or a Bug/known issue?

Would appreciate any pointers/help...

Thanks!