"Parked" orders?

Something very strange happened to Holly FTSE’s signals yesterday.

1. When his BTO signal appeared it said “Parked” for about 30 minutes. What does this mean?

2. Then, when he sent out a limit close signal, it also said parked (for 12 hours). This one is still on his page so I can copy it here:

Park until 8/16/2007 03:01: Emailed, trade pending

3. His Stop signal did not appear at all (it is still not on his page nor was it emailed). Eventually we received an email to Stop, but this was after the FTSE had crashed through Holly’s desired Stop level.

Are such occurences frequent? And what is this “parking” story?