What is the solution for the error message "Failed to save file as: could not find file, etc, etc?" (See Description for further detail)

I am a new user of SDL Studio 2015, using the evaluation version. My first attempt to work in the product failed. When I attempted to save my file, I received the following error message: "Failed to save file as: could not find file C\Users\Mark\AppData\Local\Temp\tmp\D866.tmp\  .

I consulted the Knowledge Base, which seemed to indicate that  I should install the Studio-KB8124-3.zip package. I have attempted to do so several times, only to receive a Windows Installer error message saying, "The upgrade patch cannot be installed becaue the program ot be upgraded may be missing, or the upgrade patch may update a different version of the program. Verify that the program to be upgraded exists on your computer and that you have the correct upgrade patch." Can anybody please advise?