Go to
GStudio8 -> data -> options.scr,
open it with a text editor, find
EXCLUDE_RESOURCE = "WRS;TMP;AVI;MPG;MOV;DLL;C;H;XML;LOG;TXT;PNG"
and remove
TXT
to include txt files in the WRS as well. Reason for this default setting probably is that you cannot use file_open_read on txt files which are contained in the WRS. You either have to extract them first (file_copy or what it's called) or (probably better) use file_load.