AVG released a update last week which reports a Trojan virus in certain QuickBooks and then moves them to the virus vault.  After this action, QuickBooks will not open.  After research, Fast recommends the following fix:

Follow these instructions to update AVG to the latest virus definition:

1. Open the AVG Anti-Virus User Interface
2. Click on the Update now button on the left part of the AVG user interface
   or
3. From the Tools menu, select Update

Important: Always make sure to download the latest virus updates so that you are always protected

To set up an exception in the AVG Anti-virus settings to prevent the QuickBooks directory from being scanned:

1. Close QuickBooks
2. Open AVG Anti-Virus User Interface
3. Double-click Resident Shield.
4. Click Manage Exceptions
5. Click Add Path on the right and add the path C:\Program Files\Intuit. (If QuickBooks is installed to a different folder, please add that folder path.)
6. Click OK, then click Save Changes

If necessary, you may need to restore any QuickBooks files that AVG put into it’s Virus Vault.

To check to see if any of the QuickBooks files are in the vault and restore them:

1. Open AVG Anti-Virus User Interface
2. Click History from the top menu bar and select Virus Vault
3. Locate any QuickBooks files and select one file at a time
   • Possible files include: qb.exe, qbw32.exe, qbdbmgr.exe, qbdbmgrn.exe
4. Click Restore located at the bottom of the window
5. Once finished restoring all QuickBooks files, click Close
6. Close AVG Anti-Virus User Interface

Reboot your computer and now you should now be able to open QuickBooks.