[TYPO3-english] pagtree context menu disappeared after upgrading

[Gábor Horn]

Hello,

i have upgraded my Typo3 installation from 4.4.7 to 4.5.11 LTS version. 
Since then i have no context menu in the page tree, nothing happens if i 
left click on the items in the pagetree, althought drag & drop works in 
it. I deleted my browser cache, and it doesn't work with Firefox nor IE9 
private mode, so i don't think it's a javascript cache issue on my side. 
As i know the pagtree went through a massive refactoring between these 
two releases - and this typo3 installation is quite complex (inherited 
it from other developers) so there might be local settings here which 
affects the context menu, althought it does work with the 4.4.7 version. 
Any hint please where i should check?

thanks, Gabor Horn

ps.: clicking on an iocn in the pagetree doesn't raise any javascript 
error according to my browser js debug window.