Apparently, your .tra file (which contains all strings) is missing. Try re-downloading.
I'm using the GOG version. When I run the setup file, after choosing my language I get a series of error claiming "no translation provided for @-2000" and all the files are refereed to as "undefined string." Any advice?
Otherwise...
What OS are you using, where is the game installed?
Please post setup-pst-fix.debug file (or whatever it's called, there must be a file with a similar name)
I tried downloading it again, same effect. I made a GOG folder and a planescape folder withing that, so it's not in program files or anything sensitive. I'm attaching the debug file. Thanks so much for your help.