Ok I found what’s wrong : my AD Blocker is blocking this part of the server. I added it in the white pages and now it works.
It’s strange as it has been working well for month. Probably related to a filter update of AD Blocker.
[EDIT] : For the records, the culpirt is the filter Fanboy’s Social Blocking filter which is often included in the meta filter Fanboy’s Annoyances. I think the filter is triggered because the menu entry code probably contains a term that is something like share…
