mpg files have blank video but sound present

problem seemed to just manifest itself without any changes on my side such as upgrade of klite software. I've also tried upgrading to latest but no luck there either.

Which player?

xnview classic in my case.

Codec Tweak Tool > Preferred decoders > MPEG1/MPEG2 > Use Merit

If that isn't enough:
Codec Tweak Tool > Preferred splitters > MPEG > LAV Splitter

hmmm, still no luck. neither mpeg nor mpg files are showing video in xnview with both settings changed.

EDIT: Some mpgs are working. but still a few remain that dont

Do you see the LAV icons in the system tray (right-bottom corner of Windows) during playback? If the red icon is there is means video is being decoded, and the issue is with the rendering.

If you open two instances of xnview and open a video in both, does the second instance show video? If that is the case the problem is caused by your graphics driver. There was a similar problem with IrfanView and certain NVIDIA drivers on Windows 10.

Test if the files play correctly with the GraphStudioNext tool from K-Lite.