Cashy of stadt-bremerhaven.de released a *.dll file fixing the problem.
Here’s my mirror: http://files.ainotenshi.org/liboscar.dll
All you have to do to apply the fix is to put that file into your main pidgin folder, replacing the old one.
EDIT: This fix isn’t neccesary any more. The Pidgin Project released a new version of their popular client.
Ubuntu users can get a deb on http://www.getdeb.net
Fedora 8 or OpenSuse users get their rpm from http://rpm.pbone.net/, just search for pidgin-2.4.3