Analog phone detects new phantom call on reboot

Every time I reboot the box containing my Digium card (wctdm with fxo and fxs) the analog phone connected to the card starts flashing as if a new message has come in. But there is no message. Each “call” is from itself. Is it trying to tell me something or is this just a bug? (Linux openSUSE 11.1, asterisk dahdi 2.2.0)