Calendar won’t load next months anymore

I have two calendars on my website, both were working fine a month ago.

It is set like this : <p>[wpbs id=”1″ form=”1″ title=”no” legend=”yes” dropdown=”no” start=”1″ display=”3″ language=”auto” history=”0″ tooltip=”1″ month=”0″ year=”0″ selection=”multiple” autopending=”yes” weeknumbers=”no” minimumdays=”2″ formposition=”below”]</p>

But now, when clients try to look months ahead of months showing, it brings them to top of the page, and they cannot see next month after april.

Is it a problem with the plugin or with the theme? And why did this happens all of a sudden?

Hope someone have a clue!