My guess based on what I saw was that if the limit order was close to the actual adjust, by the time your order was looked at, the price had changed enough that the trigger no longer applied.
For example, imagine STOCK halted at $17 and was going to adjust up to $20.03 and you set a limit order to sell at $20.00 but then when trading resumed so many people had queued orders to sell that by the time your limit order was looked at the price had dropped to $19.50 and so it looked like the $20.00 goal had not yet been met so the order was not processed.
This is what appears to have happened with a number of my limit orders (or at least it's the only thing that I can figure).