OK. I've posted on our guild thread regarding this to have people post more detail about their failures. Will advise as I get more. Thanks for looking into this.
I had people complain about this once. What was happening is that they were looking at the main page to see if they were signed up by mousing over the date before reloading their browser. The mouseover for the calendar does not automatically update after you sign up for an event.
The second thing people were doing was signing up as 'Nobody' since its the first thing in the drop down list when you sign up for a raid.
Prior to recent changes... you used to see your signup on the calendar event right after you submitted it. You now must close and reopen the day to see yourself on there. If you press submit again (in an attempt to see yourself ) It removes you from the entry. I bet some sleepy/lazy/half attentive people must have hit the submit a second time and removed themselves from the event.