I got a working scss (css/foo.scss) in a working solution (D:\My Documents\Visual Studio 2013\Projects\project)
When I open the solution as if it came from a network (\computername\D$\My Documents\Visual Studio 2013\Projects\project then sass compilation fails saying
Compilation Error occurred (see error list to navigate to the error location):
Error found:
Code: undefined Message: File to read not found or unreadable: (\computername\D$\My Documents\Visual Studio 2013\Projects\project\css\foo.scss
If I copy/paste the path in file browser then it opens flawlessly. AFAICT there's no problem with this file (read only, lock...)
VS 2013 update 4