I have a Siemens Gigaset 2420 for a few years now. It has some very nice features. It has a two-line desk phone that serves as the master station for the system, as well as one 2.4 GHz cordless handset (model 2400) with its own charger base. One can expand the system by adding more cordless handsets (up to a total of eight) and registering them with the desk station.
Once or twice since I have had it, the desk station would shut down on the second ring of an incoming call. All the buttons would light up and then reset itself and repeat the process on the next incoming call. In the past when this happened, I would just unplug the base station for a few hours and somehow, it would come stop doing it.

Last Friday, after a short power failure, it did this whole shutting down thing again. I did what I have done in the past but nothing happened. I even tried to unplug the base station for more than 24 hours! Oh, so frustrating....

I went to the Siemens' website but I did not find anything. I tried to re-register my handset thinking it was all it needed. But that did not help. Then, I had a crazy idea. I figured, maybe it needed help clearing things in the memory .... I deleted all the entries in the caller log. Viola! My Gigaset 2420 started to work again. It was a wild lucky guess, but it worked... I wonder if it is a bug in their firmware...

So, if you are an owner of a system like mine and you stumble upon this very frustrating behavior of your Gigaset 2420, try my trick. It might help. If you have other tricks, send it my way.