Portfolio links do not work

Hello,

I have some portfolio entries that does not show up when clicking in the portfolio grid. Instead a message telling that the entry is not available shows up as a result. Even when editing the porfolio entry I can’t even preview it (same result). The only means I have found is to unpublish it and then, as a draft, I can preview the entry.

What I am missing here?

Thanks.
-Rafa