The issue you're having should not be occurring if the new RealPlayer update installed correctly. Thefore, I would advise you to perform a clean reinstall of RealPlayer and then try downloading videos again:
1. Uninstall RealPlayer as explained here: Uninstall and reinstall RealPlayer on Windows
2. Delete the RealPlayer folders as shown here: Delete the RealPlayer application folders (clean uninstall)
3. Restart your PC.
4. Download a fresh copy of RealPlayer from: http://www.real.com/