Actually, there is a way to remove items from the list:
* From OptionTrader, click Configure on the toolbar. (If you have hidden the toolbar, click the wrench icon on the Quote Panel line.) The TWS Configuration dialog will open.
* Select "Quote Panel" in the "OptionTrader" section.
* Select the "Quote Elements" tab. Items in the drop-down list can be deleted from here.
Deleting the GC item that does not load properly should solve your problem.