.MOD is a proprietary format used by JVC, Panasonic and Canon and RealPlayer doesn't recognize and is not compatible with. Unfortunately, there is no workaround for this.
You could try to install certain codec packs. Installing the K-Lite codec pack often helps to fix issues related to playback. You can install it from the link below:
After installing the codec, restart your computer and try playing the videos again.
If it still fails, there is nothing much we could do.