Something recently happened

When I click Preferences: conversions: output settings,
Calibre crashes:
AppName: calibre.exe AppVer: 0.7.46.0 ModName: qtgui4.dll
ModVer: 4.7.1.0 Offset: 004a5c17
Was 7.47 on XPpro SP3,
Rebooted. No Joy
Un-installed and installed 7.46 No Joy
Ideas?
Note Input and common conversion settings usage are OK