I just submitted a bug in bugzilla : 34321, here is its content, maybe someone will be able to help us...

Strange bugs appeared today:

- a user plan a meeting with a location and another person participating. The other person never received the confirmation mail, but appears as "accepted" in the program view of the meeting, but is shown as "free".... and it doesn't show on its calendar, just on the meeting creator's calendar.

- another meeting, also with a location and a participant. The participant sees the meeting, accepted it, but not the creator doesn't see it anymore... he is still marked as creator but not included in the meeting anymore... and he is now free for this period on his calendar.

- some users complain about locations disappearing from a meeting: a meeting is planned with a location, the user receives a mail from the location telling the meeting is accepted, but when the user looks at his calendar, no location is shown, but on the resource agenda, the meeting is still ok... this is quite annoying because the creator does not necessarily remember the room he booked, and the other participant never see where the meeting takes place.

The big problem with this bugs is that they seem to appear randomly, I just can't predict when or why it happens. This is really a major issue since calendar is a very used feature, and there are more and more complaints about it...