As noted on my blog, we have released Firmware Patch v1.0
Use the online patch tool instead of the original tool.
To use:
Download the D5100 firmware
Download the FirmwarePatch tool
From a command prompt run the patch tool with the first argument pointing to the location of the above firmware
Copy the resulting output to your SD card and remove the ".patched" extension
Upgrade firmware from D5100 menu, as per the normal Nikon instructions
This should not brick your camera, but if it does I and the other Nikon Hacker team members will not have/take responsibility for any damages or liability. I have this firmware on my camera, and have taken a 25 minute video with it, but result may vary. Also damages that may occur due to camera operation times longer than specified by original manufacturer are your responsibility.