What would cause one particular Excel file (workbook) to repeatedly not appear among the taskbar list of currently open Excel files?
I frequently have 5-10 Excel instances containing over a dozen Excel files open at the same time. Even though I know it is running, one particular file is frequently not included among the pop-up list of open workbooks which results from clicking the Excel icon on the taskbar. (The list to which I'm referring is most commonly displayed as a row of thumbnails just above the taskbar and only becomes a pop-up list after a certain number of files have been opened.)
On some occasions, the file is present on the list but in those cases, unlike other files for which the specific filename is displayed, this file is displayed only by the name, "Microsoft Excel." At other times, it is not included at all.
Any idea what characteristic of an Excel file would cause this behavior?
By the way, this is an ongoing behavior. In other words, it is not solved by restarting Excel or even by restarting my PC.
PS FYI, I'm running Windows 7 & Office 2010.