Avira AntiVir Premium error message during the installation process

Installation of Mail and Web Protection wouldn’t follow through on my system that runs a PGP Desktop with 9.x and 10.x.
The error message during the installation process of Avira AntiVir Premium indicates that it is caused by the failed installation of LSP.

It recommends that I should “repair the LSP stack and then reinstall Mail Protection and Web Protection via the user-defined installation.” How can I find out which user it is referring to?
What are the main reasons for the failed installation of LSP?
