It could be a corrupted Windows file. Rundll32 is a kernal component as I recall and a problem there is serious-not fatal just serious.
Either do this:
Use Ssystem Restore and 'backtrack' your system to an earlier, stable state.
First off download and install Driversweeper.
Then download the latest drivers to a safe location.
Uninstall the existing drivers and restart in Safe Mode.
From Safe Mode run Driversweeper and clear out the bits left over by the lazy uninstaller.
Restart normally and install the downloaded drivers.
This should cure any faulty driver installs and get rid of any corrupted files.
Do a Windows Repair through the Recovery Console.
Be warned, although your programs should be uneffected all updates will need to be reinstalled, including any updates to Explorer and Media Player.