Either at reset; OR
When the number of IPO shares are sold long. (Whichever occurs first.)
For example, DRTYW is IPOing today (Tuesday). On the stock page is says "IPO Info: 10,000,000 shares are offered at the IPO price of H$4.00. 9,260,258 shares are still available at this price!"
So once 10,000,000 shares of DRTYW have been bought long the price will thaw (unfreeze) and will begin responding to transactions normally. That is probably what happened with BLAWH sometime late Monday.