I did run FSO.Debug.exe, FSO.IDE.exe and FreeSO.exe. After deleting the Windows-directory, FSO.Debug.exe still complains about the missing path and the other two still have this error:
~/TheSimsOnline/drive_c/Program Files/Maxis/The Sims Online/TSOClient$ mono FreeSO.exe
[ERROR] FATAL UNHANDLED...