Yes, the cairo-dock menu appears when using Firefox, when the mouse passes over the lower screen. I have VL 7.0 Gold installed on my desktop, with Xfce. I am used to the cairo-dock menu there. As VL 7.0 SOHO is on my laptop, with I believe KDE desktop (or a modified KDE), I did not expect to see the cairo-dock menu. When I installed VL 7.0 SOHO on the laptop, I replaced VL 7.0 Gold. However, I created two partitions "/" and "/home" and formatted both. (Sorry, I can't provide a screen shot because the issue is on my laptop and I don't know how to do it). If the cairo-dock menu is part of the SOHO version then fine, but I rather doubt that it is part of the KDE.
Go to your KDE Menu, Applications, Graphics and use KSnapshot to take a screenshot.
I seem to recall Cairo being active when I first installed SOHO 7. One of the first things I did was go into System Settings and disable it.