Here is the only fix I know
This should let you download zip files through your browser.
Download the free Astro File Manager from the market.
Launch Astro, hit menu, then more, preferences, at the bottom of the menu is a Enable Browser Downloader check this.
This will allow you to download all different types of files through the browser. They say is can make some downloads in gmail not work so if you have any problems with gmail downloads make sure you remember to turn this back off. Honestly I haven't had any problems with gmail so I'm not sure what it can cause to mess up. I leave my option check all the time in Astro.
Hope this helps!!