>but no signal seems to be received when I push Pc or aux buttons.

Make sure you selected 'Enable mode keys' during the setup.sh process of installing LIRC. 

You may also want to tweak the remote's behavior in its module parameters.  In the LIRC source tree, under remotes, find the source code for the ati remote.  In that c file near the bottom, you'll find the possible module params defined there.  Some are mdeadzone=n, mgradient=n, enable_updown=n, etc.  There are enough comments in the source code to get a hint of what those are an what values they expect and their behavior.  Enter those parameters while loading the remote's kernel module either using modprobe, or modconf (preferred).  Good luck.  RC remotes rock!