Keynote Save Problem

Hey guys,

All of my teachers use powerpoint to make their lectures and I just download them and convert to keynote's format. This has been working fine for the past year, but just recently, whenever I open a downloaded powerpoint file (usually .pptx) and try to save it, Keynote gives me this error:

The file "______.key" doesn't exist.

Additionally, when I try to create a New Folder from the Save drop menu in Keynote, it states that the folder is "Read-Only", thus not allowing me to create a new folder. BUT, when I go into Finder, every one of my folders is Read-Write permission granted, and I can also create a New Folder from the Finder menu. So the only problem is with Keynote somehow "thinking" that my folders are Read-Only. Any thoughts/help??

Running Yosemite, OS X 10.10.5 on a Macbook Air bought in 2014. Keynote is most recent version.

Andrew