With Chromium and Chrome recent versions 12 and 13 there is a pb with some sites such as Gmail. ABP makes time to run : the browser waits a while before blocking sites and displaying ABP icon.
In Gmail the pb occurs when there is new mail received.
To unblock this and make ABP icon appear, it is necessary to interrupt the transmission (X button)
Maybe this pb is due to Flash Player 10.3 (it seems dating from 10.3 installation) ?