Attempting to use the Toad for SQL Server print button while Report Designer is open causes System.InvalidOperationException.
Steps to Reproduce problem:
1. Select a column or a cell, right mouse click, open Report Designer.
2. Select standard report, select at least one column, then select finish.
3. The report will generate onto the screen. Try to print by going to File | Print and you will get the exception.
Report Designer has its own print button for printing reports. When the report is open, click on the "Preview" tab at the bottom of the screen. Then click on the Print icon just above where the report is displayed. Use this print button instead of Toad's print button from File | Print or the Print icon in the Toad Toolbar.
Waiting for fix in a future release of Toad for SQL Server.