The BB is designed to not allow you to download large files like that. Larger files from the Internet are not downloadable from the BB Browser either. I guess it's RIM's way of CYA so that they don't get pegged with data overage charges from different carriers.
There was a hack a little while ago (a few months back at around the time ~5.0.0.119 came out) that had you replace a couple browser modules with some programmer's "special" and "customized" modules. After that and a few tweaks you were supposed to be able to download anything and everything. I wouldn't suggest this route since this "module" could, more or less, be anything and do anything to your device.
When I realized that this required me to swap trusted files with some stranger's files I lost interest in this. If you're still interested, proceed at your own risk. There was a blog post about it, so I would go to the main page (the CrackBerry Blog) and skip twenty-something pages until you find the post about the 9530 5.0.0.119 leak. It happened immediately after that.
I can also get you a link if you want, but that would take some time.
