You may have added an item under "Materials" that you want to delete, but can't. (below). If this is happening to you, do an export of your items, by going to your login name> settings> quotes and quote items.
This will create an excel spreadsheet with a page for each of the categories you have under Quotes.
The solution is simple. Once you've exported, find the item in the excel sheet. Change the delete option to "yes", save the file and re-import. That will remove the item.
