babak,
new issues need to be entered into a database and out of the literally thousands of new markets added each day (40+ global exchanges and all the associated options strikes, splits, etc) things can be missed. Most of the process is automated but things do get overlooked. If there is an IPO coming up that you want to participate trading on the first day, I'd suggest sending an e-mail to the help desk with the details (stock name, symbol, date of IPO). This hopefully will help getting it into the system on time.