I managed to solve it! If anyone comes accross the same problem, it can be solved by adding the following code to Quick CSS:
.html_header_sidebar #header .av-main-nav li.current-menu-item > a:hover .avia-menu-text{color:#ffffff;}
Ok I had missed something indeed: I had not defined my meny in the wordpress admin… RTFM as they say.
You can close, sorry about the noise.