It's more likely to be the inductor that's the problem.
If that's not it - then the layout is something to check. Circuits like this can be crirital on component placement. Use the datasheet of the LT1073 as a guideline.
Also, you do not mention which version of the LT1073 you are using. There are 3 versions.
LT1073 - adjustable
LT1073-5
LT1073-12
I would assume (dangerous, I know) that you would want to use the LT1073-5 to get the 5-volts that you are wanting.
Pretty cool idea - and a cool circuit. Let me know how it goes.
Regards,
James Jackson