After update of Ubuntu RT redirects to installation page

We have been running RT4.4.2 with mysql backend and apache for over a year now without problems.
Today I updated the ubuntu packages on this server and suddenly the RT install redirects to Install/index.html.
What happened and how do I fix this?

Well it seems that an update reset all the directory permissions on /etc/request-tracker4/RT_SiteConfig.d
After fixing that the problem was solved.