I've also checked the area where I park my bike and can't find anything. The only thing that changed, was that I cleaned up around my utility trailer. But even there, I made sure that I did a thorough sweeping (several sand bags that I have, were used for weight in the back of my truck in the winter) to ensure there was nothing that could potentially puncture a tire.
This is really cheesing me off, given the limited opportunities that I have to ride. =( I really don't need this further cutting into my ride time. The tires are the Trail Wings (AKA "Death Wings") that came stock with my WR. The front tire looks fine. No cracks, or stuff stuck in the tire.
Picked my bike up from Yamaha. They checked the tube, only to find out that it was defective. The inner tube was replaced free of charge. =)