"ORA-12154: TNS:could not resolve the connect identifier specified" (but under Windows XP 32-bit all OK).
And here is the simplest solution:
run TOAD via command line using short path:
instead of long:
C:\Program Files (x86)\Quest Software\TOAD\TOAD.exe
Unfortunately Windows doesn't allow to change desktop's shortcut from long mode to short (Windows always expands short paths).
Or... move TOAD from "Program Files (x86)" to "Program Files" directory.