Each time you download something from the internet using firefox browser you will see the download gets stuck by the time it reaches 100% this is because firefox scans each file after downloading. How much of that scanning is effective I am not sure. But if you wish to disable this scanning function because you have a good antivirus, here is how you can disable firefox file scanning after downloading on Windows Vista Xp and Windows 7.
Step 1:- Open firefox in the url addressbar type about:config and press enter. It will confirm you about your actions press “I’ll be careful, I promise! button”.
Step 2:- Now type scanwhendone in the filterbox, and press Enter you will see an entry named “browser.download.manager.scanWhenDone” in the bottom half of the list.
Step 4:- Now our aim is to set its value to false. You can do that either by double clicking the key value or by right clicking and selecting “Toggle” and set its value to false.
Step 5:- Close this tab you are down you will see the effects immediately if not then restart firefox. No more will your firefox scan files after downloading and get stuck