I still have an old oracle "(x86)"-cursed version on my machine - reminds me to your problem.
Connection fails when the executable has special characters in its pathname, like :
C:\Program Files (x86)\Sybase\PowerBuilder 11.5\PB115.exe
If I start PowerBuilder via command line using 8.3 pathname syntax then the connection is o.k..
c:\progra~2\sybase\powerb~1.5/PB115.exe