Because the updating process needs to copy files into your Program Files(x86) folder, you need to give your computer explicit permission to do so. Because of this, automatic updating of Hellfire can sometimes fail, and has been one of the main causes of erratic behaviour and random error messages in the past. Indeed, many people have opted to turn off automatic updating in favour of just downloading the full install every time there is an update.
Starting with Hellfire V3.6.1, there is a completely new updating mechanism, which displays its progress to you, and will also let you know if there is a problem trying to update.
Firstly, ensure you have updated to at least Hellfire V3.6.0. This will require downloading a full install, once auto updates are turned back on, versions prior to V3.6.0 may not correctly update using the auto update mechanism.
Next, make sure you have auto updates turned on (it is turned on by default, but please consider re-enabling this if you have it turned off, unless you experience issues with anti virus programs complaining).
To ensure auto updates are enabled, select Game Settings from the opening screen and select the Updates tab. Make sure the Check for updates Automatically on Startup option is ticked.
Close the screen and Hellfire will check for updates. If there is an update available, you will see a message at the top right of the opening screen.
Click on the message to launch the updater.
Click Yes to start the update. The updater will wait for Hellfire to completely shut down (this can take a few seconds after Hellfire disappears from view) before it prompts to download the update.
Once the update has finished downloading, the updater will prompt you to close it.
Hellfire has now been updated and you can start it as per usual.
Sometimes the updater cannot access a file it wants to update. If this happens, the updater will stop and display a message saying it is waiting to unlock a file. You may also see a Windows error message detailing a 'Permission Denied' error.
In either of the above situations, close the updater using the red cross at the top right of the window (or click Close on the 'Permission Denied' window) and restart Hellfire. Try to run the update again by clicking on the update message - it should run successfully this time. If you don't have any luck after retrying a few times, let me know (I've tried running this many times and if it doesn't run the first time, it almost always works the second time).