Verification Error

I started getting this error while trying to upload a sketch:

avrdude: verification error, first mismatch at byte 0x0200
0xb0 != 0xff
avrdude: verification error; content mismatch

I have verified that the correct board is selected in the IDE and tried different USB ports on my computer. Any other suggestions? I understand this may be a problem with the bootloader, but I am unclear on whether I can re-burn it from the IDE or need special hardware.

Which board/processor, original or clone, and any shields attached?

It is an Uno R3 SMD board that came in a SparkFun Inventors kit (which I assume means it is authentic).

No shields attached. It first exhibited the behaviour when I was running a simple test sketch for an ultrasonic sensor. I think the sketch loaded the first time, since the pin 13 LED was dimly lit (sending short trigger pulse), but I tried to load the sketch again after a tweak and got the error.

I tried loading the Blink sketch and same thing.