Problems to connect to modem after internet break down

I have a Digi One SP (located in DE) and to this I have attached a modem (9600 baud) and it is also located in DE. I use the RealPort settings (latency optimized) and my server is located in DK (I use the modem as a dialin solution in Germany).
I have this problem, that when my internet connection breaks down (it happens), I can not get in contact with my modem again before I reboot the Digi One SP and deactivates/activates my DigiPort driver on my Windows!?
How do I solve this problem, so my modem and server automatically can communicate even after a internet breakdown?