If I'm not mistaken, we shouldn't need NDISwrapper (nor any .sys or .ini files) for a 4312, since either the wl driver or the STA driver should work. So the short answer is "yes", if you want to download something to Windows, then transfer it to the Ubuntu partition, you can do that no problem.
Just boot Win, download what you want, then boot Linux and mount the Windows partition, locate & navigate to the stuff you downloaded, and move/copy it to your Ubuntu system.
Note that the wl driver may already be present on the Ubuntu system; the STA driver however, you must get from Broadcom, and then compile & install it.
If this doesn't help, or if it's a different driver you believe you need, please provide further clarification.
PS - I'm not clear on why updating your Windows OS has interfered with your wireless from the Ubuntu end of things.. Maybe there's more to it than meets the eye, like maybe Windows shutting off the wireless device when it shut down, and Ubuntu not turning it back on.. Anyhow, if necessary, we'll dig deeper into this.
Last edited by GrapefruiTgirl; 07-19-2010 at 11:05 AM.