Q: After updating my avast! Home/Professional to version 4.7.826, it no longer works. If I try to run it, it doesn't seem to be doing anything, or displays an error message.

A:

Unfortunately, version 4.7.826 contained a bug that could, under certain circumstances, cause setting of incorrect access rights on the avast program files, preventing the program from functioning properly. Namely, the problem may occur if any of the following three conditions is met:

• the operating system was previously updated from Windows NT 4.0; or
• avast was installed in a different folder than the default Program Files folder (that was offered to you by the installer); or
• previously, the system volume was converted from FAT32 to NTFS.

Solution
In order to correct the situation, please take the following steps:

1. Uninstall avast! using the avast! uninstall utility (this is more reliable than the Add/Remove Programs applet in Control Panel).
2. Restart the computer.
3. Download the latest version of avast! from our website:
   
     - Professional Edition: download from here.
     - Home Edition: download from here.
   
   and install it.

The latest version does not have the problem, and should function correctly.

We apologize anyone who faced this problem.