Apart from playing with geeky hex editor :) You can fix that issue much easier, just:
- Download the already fixed Pidgin Facebook plugin (“libfacebook.dll”) from here: http://bit.ly/pidginfacebook .
- Put it into the “plugins” subfolder within Pidgin installation directory (e.g.,
C:\Program Files\Pidgin\plugins
). - Launch Pidgin - the error message should not occur anymore.