I actually have problem focusing at 41mm to 44mm at all times. The camera would lock up and focus is gone. Sometimes it'll come back, but other times, I have to turn off the camera and quickly zoom out of that range before focus comes back and lock up again. I tried many options such as turning off continuous-focusing and no luck.
I'm able to "step" around it by just moving backwards to zoom back but otherwise, I have to avoid anything below 44mm. I could go to the service center to have it cleaned/fix, but since I've never sent one in before, I'm thinking it's going to be very expensive. If such is the case, I'd just save my money and wait for another brand with a slow-motion niche. I liked the EX-F1 until quality issues such as this.