It appears that the first time you try to do a search that will return a lot of results something is timing out. This appears to be true both in the code I have developed and just plain loading the url in Firefox. Searches with very few results seem to work all the time. The first time I retrieve the url given the browser sits loading for a bit then just stops with no data received. Trying again usually then gives a set of results.

I think this is going to be solved by https://bugzilla.mozilla.org/show_bug.cgi?id=400986

I'm going to close this as fixed. I think restricting the returned results solved the problems here and I certainly haven't seen any failures in a long time.