Ctrl-Left-Click and Ctrl-Right-Click are defined respectivelly to open a link in a new layer or in a new layer in background.
To bypass this, choose the mouse Accelerators that you want :
Menu Tools > Mouse Accelerators > Firefox 2.0 or Seamonkey 1.1
A+
Mozilla/5.0 (x11; U; Linux x86_64; fr-FR; rv:38.0) Gecko/20100101 Ubuntu/12.04 K-Meleon/76.0
Web:
http://jujuland.pagesperso-orange.fr/
Mail : alain [dot] aupeix [at] wanadoo [dot] fr
Ubuntu 12.04 - Gramps 3.4.9 - Harbour 3.2.0 - Hwgui 2.20-3 - K-Meleon 76.0 rc