When did you last use this? If I remember correctly the method used tom play DVDs was changed after the System Menu v4.3 (June 2010) update, and you need IOS58 to use the new method.
But I am not sure, I only played a DVD once for a view minutes as a test years ago and never used it as a DVD player, I have enough other devices for that.
Best look in the documentation of WiiMC how to set up DVD playback now or try a different Wii media player with DVD capabilities.

 

if you have an older wii get ios 58 no patches have HBC 1.0.8 or higher version and download wiimc put in a dvd and play it from the disc option in wiimc

 

Make sure you are using the latest HBC and IOS58. That will give you AHBPROT, which is total access to the Wii (hence DVDX is useless). Also check meta.xml to make sure you did not comment out AHBPROT.

 

Nintendo lens cleaner, although it looks like they quit making it, I bought one at gamestop a few years ago. Works wonders for dual layer disc games and dual layer disc DVD movies.

http://store.nintendo.com

 

It was probably the effed up gamestop worker that effed up the Wii while cleaning the lens. I had no problems cleaning my lens with the Nintendo brand lens cleaner, I think I bought it because the Other M game I rented wouldn't work, upon cleaning the lens the game worked.