I have 'rolled my own' theme and on returning to Themeroller by pasting the url, I find that the Download button does not work. What I am I missing?

UPDATE:

As a work around I tried to Edit an existing theme. After some time the Download button was disabled.

I pasted my original URL back in, reloaded the page and right-clicked on the Download button. I could then open the link (ie the download builder page) in a new tab. That enabled me to complete the download.