For the time being lwjgl.dll has been added to avg virus database.
This is not true the file is 100% safe. Here is a scan using 43 Different top of the line anti-virus scanners.
virustotal
My best guess is a couple guys thought it would be funny to spam AVG with reports saying this file is not safe. After enough reports the file gets marked even before they have a chance to check it themselves. Once the AVG has caught on and fixes this it will be marked as a virus.
Solution:
1.
Mark the lwjgl.dll As safe. It's location is %appdata%\.minecraft\bin\natives
If the file is not there. It has been moved to quarantine. You must navigate through AVG to find the recently found threats. locate lwjgl.dll and use the recover feature. Also select remove from future scans.
My knowledge of the AVG menu is limited as I don't use it. If someone can update exactly how to remove something from quarantine and mark as safe it would be appreciated.
2. Disable AVG before you play minecraft may need to re-install minecraft if the lwjgl.dll has been moved to quarantine folder. To reinstall go to %appdata%\.minecraft and delete the bin folder. Upon launching the game it will download and install everything.
3. Uninstall AVG and find another antivirus. Personally my favorite

but it's entirely up to you what antivirus to use.
***EDIT:
Just finished installing and figure out AVG.
To continue to play minecraft is fairly easy to do.
When the virus warning first pops up. Press Ignore. It should automatically mark it as safe and you can play no problem.
If It has been marked as a virus, To recover it. Open AVG select "History" in the top tab, and go to "Virus Vault" Click on lwjgl.dll and click "Restore"
If you want to make sure the file is excluded from scanning and any modification by avg do the following:
In the AVG main window, select "Tools" in the top tabs, then "Advanced Settings" In the new window that opens, Under "Resident Shield" there are "Excluded Items" Click on that, and select Add file or Add path, depending on if you want to make just that single file safe, or the whole minecraft folder.
Here's the location to the file (copy and paste this in file name text bar) %appdata%\.minecraft\bin\natives\lwjgl.dll
Here's the path for Minecraft (copy and paste into Folder text bar) %appdata%\.minecraft
Hope this helps.
Copy and paste ftw