I'm dealing with the exact same problem, actually. If your Wii's as ancient as mine (it's all the way back from '06), then I'd imagine your disc drive problems are due to old age, and wear n' tear. Since your lens cleaner didn't work, that gives me little hope for my own... =/
Regardless of my problems, my guess is it's a problem with the laser itself that reads the discs, and not necessarily a dirty lens. It could also simply be damage to the drive, if you've dropped or hit the Wii prior to the problems starting. Is there a possibility you could of damaged your Wii somehow?
Before you invest in any repairs or solutions to your problem, try placing your Wii horizontally on it's side (if it isn't already), unplug all the wires for a day, and hope that solves your issue.