With PowerPoint 2013 when opening a document for edit from SharePoint 2010 or SharePoint 2013 you may see an error similar to this:
"Sorry, we couldn't find C:\users\<userid>\Desktop\%u. Is it possible it was moved, renamed, or deleted?"
This only happens when the SharePoint server is in an IE security zone that is set to use IE protected mode.
You can turn off protected mode for the IE security zone.
A fix for this issue has been released: