yes - 5100
I did as you suggested. The print head moved easily across the bar. When I switched the machine back on, it made a noise for a minute or two (re-calibrating I guess) then the blue light stopped blinking. I was just about to try printing when the machine, of its own accord, started making noises again and then the orange flashing light came on and the error code 5100 appeared. I went through the whole procedure a second time and exactly the same thing happened.
I cleaned the clear strip with a lint free cloth and then repeated the steps as you suggested. The only difference this time is that when I switched the printer on again, it re-calibrated and then the blue light stopped flashing but this time the printer did not make any further noise of its own accord and switch to the orange flashing light. The orange flashing light only occurred after I pressed the Print button followed by the error code 5100.
I repeated the whole process but the same thing happened.
The printer is over a year old and I do not have an extended warranty.