rui. i'm no vegas expert but i think i know what your prob might be.
your recording in mono BUT if you look at the properties of the track your recording to i have a feeling its probably set up as stereo. ive come across this in several multitrack software. just go into your track properties that your recording to and change from stereo to mono.then having recorded
your mono track use the track pan control to pan the track where you want it.
i hope this works for you.