Your code example shows it writing the return from get_page_source to the file that you're renaming to ".zip". I wasn't sure if some additional transformation was necessary to remove the html 'wrapper'. These are the things I would do (some of which you may have already done):

1. Download the zip file manually and verify that you can unzip it
2. If you're on a *nix system, run 'sum file.zip' and 'file file.zip' on the file and keep the results
3. Verfiy the 'content-encoding:' is what you expect
4. Once you use your script to download, use 'sum' and 'file' on the result(s) to look for differences

fnord