A bit to complicated for me, since I don't really understand javascript. But the problem seems to be a combination of your form-script and going a little crazy while naming files.
You will notice that in Explorer the following is added after the URL of your page:
#ht=764
As long as it comes after the .html extension, this is only confusing. But when you have a file name with a & in it, the addition is made there. My guess is that if you rename the page bookingform.html, the problem doesn't exactly disappear, but the page should stay open in Explorer.
