Today AVG Business (= the paid version of the antivirus software) automagically installed its new version. And, [censored swear word], after restarting my pc, no more connection between my SunSDR and my PC.
Shutting off the firewall solves the problem but is of course not really a long term solution.
I have added the ExpertSDR software and the network address of the SunSDR to the firewall settings but to no avail for now. I guess I’ll have to dig a little deeper to get it running again.
UPDATE: I messed around for a while trying to allow the SunSDR and ExpertSDR to get through the firewall but to no avail. As I use a pretty decent firewall in my router I decided to simply uninstall the AVG firewall component.