Hello guys!

how can I enable transparency for the kmenu if it is not enabled with the default settings under my old userspace (http://img2.imageshack.us/i/screenshot1qi.png/) but it is under newly created user-home (http://img181.imageshack.us/i/bildschirmfoto1l.png/)?

kind regards,
Quentin

Do you have Desktop Effects enabled in the first case? System Settings -> Desktop Effects.

Yes, desktop effects are enabled. IF you want a proof:
http://img820.imageshack.us/i/screenshot2leo.png/

On this image you will notice a second issue: my cursor is pointed on a directory, a button should appear to open the folder in preview-mode (like it was automatically the case on mouse-over in a previous KDE version). This button will appear in the new home-userspace but not on my old again. Please don't suggest to remove my ~/.kde4/!!

I have the same problem regarding the missing icon, but in my case it seems like it's a problem in the workspace theme I use. It looks like you use the default theme, is that right? In that case you can try to do the following outside of a KDE session:

1. Clear cache by removing /var/tmp/kdecache-$USER/
2. In ~/.kde4/share/apps/desktoptheme (sometimes ~/.kde/... instead), move the folder with the same name as the theme you're using to another location. If you use a non-default theme, you have to reinstall it again.