We bought our Toro from the big box store in 2009.
We thought it was a great mower until this year (2012) when the right rear drive wheel started locking up and eventually tore out the gears. $25 later and two mowings and it is starting to act up again.
Here is the deal -  there is no adjustment to tighten the meshing between the steel drive gear and the plastic wheel gear. I am unsure if it is simple wear or the wheel mounting bracket is bending, but I fixed mine by taking off the offending wheel, screwing a 3/8" x 4" bolt in to the wheel mounting hole and screwing it in until it starts to bend the bracket out. A little persuasion on the bolt with a pipe wrench or some such helps.
This will force the gears to mesh tighter and should fix that issue.

The problems with the drive may be that the adjustment for the drive engagement handle slipped - mine did as it wasn't tightened properly from the factory and it was like there was no drive at all. You should be able to walk up to the mower and keep walking and the drive takes the mower from there. This mower has plenty of power to pull both itself and you.

When storing the mower for winter, spray a bit of lube - in the wheel bolts to make sure that the water you used to wash off the mower isn't causing corrosion between the bolt and axle. This may cause the frozen wheel issue some have mentioned.

Yes I think Toro Customer service could do a better job, but they are just working in a call center and assume an authorized repair center knows what to do.

The only thing I would have done differently is buy the better "commercial" model with the black bag from the Hardware store. It looks like a better designed machine.

Recommended: Yes