The problem is definitely the boots. If the Burton cap straps don't fit or work, send them back and perhaps you could consider getting new boots from a different brand.
Vans boots have much softer toe sections than most brands, which collapse under the toe straps. This was the main problem in reviews of multiple Vans boots on The Good Ride. http://thegoodride.com/boot-reviews/vans-cirro/
Hopefully everything will work out for you.