Just a quick update - Paul tried to run files from my machine on his and the result was that everything was working ok.
So the situation is as follows: - brand new installation of RT-4.0.6 - database moved from RT-3.8.7, upgrade went well - only local changes are those mentioned in this thread, plus the RT_SiteConfig.pm and an import of one css file via css/base/main.css/End callback - $ uname -a > Linux rt-mirror 2.6.32-5-686 #1 SMP Sun May 6 04:01:19 UTC 2012 i686 GNU/Linux Any ideas are welcome Thanks, Martin