The IDM AD driver requires a filter DLL to be installed on all DCs for password synchronization. Unfortunately, it seems as if the IDM setup does not always update a previously installed version of pwfilter.dll (and associated files) properly.
This INF installer can be used to update those files so they will be used after the next reboot:
Many thanks to Alex McHugh for adding x64 support and fixing some bugs!
Disclaimer: As with everything else at NetIQ Cool Solutions, this content is definitely not supported by NetIQ, so Customer Support will not be able to help you if it has any adverse effect on your environment. It just worked for at least one person, and perhaps it will be useful for you too. Be sure to test in a non-production environment.