Hi

Just to inform that I found a solution to the problem above.
Got it from an IT guy at the company where I work.
Connect the cablecom modem and Netopia router/modem with ethernet RJ-45 cable and then unplug the cablecom modem from power supply for about 10 min. After that plug in the power cord again and wait 2 min. Few seconds later and wireless connection works again. Unplugging the cablecom modem resets the connection ad both devices automatically synchronize when you plug in the power again.

So if anyone else change internet connection from Swisscom to Cablecom can use old wireless router/modem without any problems.