Vegas Pro renders partials Ok but ALL audio.

Hello, here again for help: yesterday when preparing a slide show using SV Pro 9 I did a partial render for checking. Vegas did render the video part I wanted alright but it also rendered the full audio track. This didn't happen before, the rendered audio was normally the one belonging to the partial video, the problem with the change being that even rendering a short clip takes the same time as the full presentation and also the size of the partial file goes to 50-60 Mb instead of the normal 10-15.
I don't remember changing any settings but maybe I did inadvertently.
Assistance will be appreciated...