All error messages catched should go to the log as well as the command used to call slic3r.
Just retested slic3r with different settings in manager and it all worked.
Does the C:\Users\Name\Appdata\Local\RepetierHost\slic3r.ini get created and changed? After every slice try it should get a new date. You said the file slic3r complains that does not exist is there, so it seems to be a problem of lsic3r reading that file.
Could it be that your login has spaces or non ascii chars that cause problems? These file names always need special care especially on windows where utf-16 filenames are used. You could install Slic3r 1.1.7 in parallel and set it up in host. I guess that would also work with 1.5
