Permalinks strange behaviour

Hello guys, hope you can help with some suggestions.
I'm running a plugin named: all in 1 event calendar, which is working great on another server (with Apache), but here on this server (NGINX) is having a problem (I think) with permalinks.

If you go in the calendar page: http://blogs.eui.eu/francescomartino/calendar/
and try to change view (from month to week for example), it will get stuck in loading.

If I disable permalinks, the change view it's working.

When I set a default value in permalinks settings, a string /index.php/ is added to the permalinks structure... maybe there is a connection....

Do you have any idea?