Everytime I use VOIP, internet connection drops

misterno

I am using a wireless modem/router and no other device for VOIP. I am also using voipraider and lowratevoip as my VOIP providers. Up until a month ago, everything was fine but now everytime I dialpad with VOIP, internet connection drops in 20 seconds. So, I have to reboot the system.
ATT technical support tried to help but coould not find anything on their end but commented that; it is probably I downloaded a Microsoft patch or update which conflicts with VOIP system.
And that is true, I allowed automatic updates from MS all the time and I remember couple of patched in the last 2 months.
And by the way, I am not using any third party device for VOIP. It is only the voipraider or lowratevoip software and their on screen dialpad system.
Please help.