i have encountered this problem before myself...and this is the solution i used..
step 1)install the PG addon
step 2)change group of user nobody to nogroup (if using gnome, you can do that in main menu->system->administration->users and groups..remember to show all users to show up the user nobody) and also change the shell of nobody to /bin/bash if it is set to some other shell...
step 3)startup PG using /opt/lampp/lampp startpostgresql
(if necessary, you can also chown -R nobody:nogroup /opt/lampp ...i am not sure if this is essential)
hope it helps...
PS: a bit of searching would have given you the answer..the same question has been asked before..most of my method is derived from threads like this one