Hmm, 'kay :)
Btw, I am not sure how but got rid of the errors and the connection is not dropped and I can access pfSense's webinterface through the 552 ;D
I couldn't do any speedtests, well, I could have tried but I don't think a speedtest between my phone and laptop would show the maximum :P
(Just thought of the iperf package, but the computer I was trying this on did not have access to the internet.)
At least I know this card seems to be working with pfSense ;D , eventhough the lack of N support, but hoping this might change.
Now waiting for some antennas with cables (so that they do not have to be put away behind the pc case under the desk).
The ANT24-0230 unfortunatly is not available outside of North America (and no shops willing to ship it here ???) so now waiting for some alternative I found on Ebay. :)