I created a new event, I didn't duplicate anything.
I set the begin/end date (which is the same), I set the time, the location, chosse a category and I published it.
It's all real standard, I don't use any custom hacks or so.
I deleted the event, emptied trash and made a new event, with exactly the same details and the same way I did it before.
For now it's gone again, but it really puzzles me.
Don't wanna add each one day event, then delete it and re-add it.