There is a simple fix that will usually resolve the problem--delete the Pidgin preferences file.
- Open the My Documents folder from the desktop.
- Switch view to My Computer
- Open IMLogs on 'lib-nt1\sys2\files' (L:)
- Open .purple folder
- Delete prefs.xml file
- Start Pidgin using the desktop icon
- Reset usual Pidgin preferences and plugins (refer to instructions at Ref Desk)
- Preferences include: Logging on and LibraryH3lp plugin enabled