New AntiVir software will freeze Windows UI?

After upgrading to new Avira AntiVir, my WindowsXP sometimes stop responding requests and only mouse cursor is still alive, and all applications can't be launched and the machine is not able to be shutdown either.

In my case, restarting explorer.exe can solve this abnormal issue:
1. Press [Ctrl] + [Alt] + [Del], launch [Task Manager].
2. Find "explorer.exe" process and terminate it.
3. From [File] menu of [Task Manager], choose [New Task]...
4. Run explorer.exe again.