It just happened today as I was riding up a slope. The rubbing is so loud that I can hear it with my helmet on. I did not adjust anything. The freeplay is good and so is the chain. I'm hoping that it's not that a big of a problem so, I won't have to ride it to the shop. Thanks in advance!
The chain may look good, but it can be stretched beyond specifications.
Put the bike on it's center stand.
Pull the chain back, off of the rear sprocket.
If you can pull the chain off of the sprocket one half the distance or more than the sprocket's teeth, the chain & sprockets require replacement.
Rotate the rear wheel and check the chain ware at different spots of the chain.
At least 4 different spots.
Not sure if your bike has one – there may be a plastic rubbing block near the front of the swing arm.
They are mounted near the front of the swing arm, wrap around the front of the swing arm and is bolted to the bottom of the swing arm.
The rubbing block is used to prevent large slack chains from scrapping on the swing arm.
If the rubber stop Exo mentions is still there, I have only one explanation.
Improperly adjusted chain.
The only time I have ever had a chain rub is when it has stretched/worn and needs adjustment. The only proper way to check chain wear is with a gauge (which I do not use – I eyeball it)
Something is loose, broken, or bent.
The centerstand shouldn't be rubbing with the chain.
Climb under there and LOOK at it.
"The freeplay is good and so is the chain." So you've eliminated everything except a bent frame or problem with the center stand. Generally center stands have rubber stops. Still there? Have you checked the parts fiche? http://www.partsfish.com dude.