The report renders correctly in the iFrame, but selecting to Export (to any format) using the 'Export' functionality, I get a popup saying 'Server busy This action cannot be completed because the other program is busy. Choose Switch To ....'
I tried putting a hyperlink on the actual report stating explicitly to render to excel, but while that works from within the report in reporting services, I get the same error as mentioned above when trying to execute from within my application viewer.