Issue:
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.
Workaround:
You can turn off protected mode for the IE security zone.
Current Status:
The product group is actively looking into this issue, a hotfix for PowerPoint maybe provided. Check back to this blog for more info.