Hello, i hope someone can give me a clue for my problems. I have search the web and cant understand why some dvd copies dont work anymore. (excuse me for my basic English)

I have a wii (firmeware 4.1E) moded whit an Wiiclip-wiikey2 (v1.3 firmeware). I have dvd copies that months ago worked perfectly and now they give reading errors, or the situation that just appear in the channel menu but whend i try to play it give errors (for exemple NSMB).
In one game (Pro evolution soccer 2011) it appears on the channel menu, i cant start the game, it gives the information to plug the nunchuck controller but them it goes dark and noting appends.
Only two of my games work in this days. One is the Mario Kart the other is Broken Sword. It runs all perfectly.

All the games are burn in imgburn at 4x and all TDK dvd-r are without any surface damaged.

Can it be the lens of the DVD player? And if it is I does two of my games play normaly, other are read by the channel menu?
If anyone could give-me an advice, i would be very happy.

Thanks in advance.