I have been bounced from every department of service for 2 hours. I use Task Scheduler to open an .xlsm file. Despite having addressed the association of the file first with the windows 8 pop up "How do you want to open up this type of file (.xlsm)" where I did select the checkbox "Always use this for this type of file" (paraphrased) as well as selecting the association through the right click on the file - Open with... option, I continue to get the "How do you want to open up this type of file (.xlsm)" when the file is being opened by task scheduler (defeats the purpose of automation!). I am able to open the file without the message when opening manually.
This was NOT an issue with my Windows 7 / Excel 2010 PC.