This is exactly what happened to me. It occurred while playing Call of Duty: Black Ops, but I had played the game before; my system automatically shut down while playing online and now it can't read any disks, Wii or otherwise. Games downloaded from the Wii Shop Channel still work fine.
I sent my console in to Nintendo for a repair and they sent it back, claiming that it was "bricked". However, judging from the definitions on this site and the state that my Wii is in, it is not technically bricked. It's possible, I suppose, that the Nintendo technicians found the homebrew I had installed and immediately assumed that was the problem.
I'm posting this here because I did update Homebrew Channel and many programs on it (Homebrew Browser, Code Downloader, Cheat Manager, Gecko OS) shortly after I bought Black Ops and shortly before it crashed. I also had to update the system using Nintendo in order to play Black Ops, so the new system menu might have collided with a malfunctioning new version of my programs to overheat the game, or something. The problem is that I had no homebrew running at the time I was playing. I don't even have BootMii installed.
Many people have complained on the Call of Duty forums about this happening to their Wii while playing Black Ops, and many of these cases seem to involve homebrew. It seems that the game puts more stress on the laser than most games do and homebrew just helps it to break more easily. I just want to know whether I'll have to purchase a new Wii (and lose all of the data that I can't back up) or buy a new laser and install it myself, because I doubt it can be fixed using only programs. (a laser cleaning kit had no effect)