No, James, the solution you proposed didn't work. I CAN get to the spreadsheet I want but only after going through hoops.
It happens with all the sheets either on the hard drive or finger drive. I am using a Lenovo computer with Windows 7. I don't have the problem with other computers. Could it have something to do with the difference between 64 bit and 32 bit computers? For what it's worth, the problem only arose recently; it used to work well.