Ruatha, most likely my advice is stupid and incorrect, but afaik pbw will accept only quoted path in the form, ie
'c:\games\se4\savegames\blah_x.plr'
or with double quotes:
"c:\games\se4\savegames\blah_x.plr"
(i don't remember which variant is used, and pbw is offline at the moment, so I can't check it).
I don't think this will help, but you can try
