Conflict Between USB Input Device And Digital Receiver?

I do use a online USB foot pedal that is used for transcription. I have two plugs powering the system, one for the monitor and the other to the CPU, connected to a extension cord with 5 sockets. To the rest of the sockets I had my DTH (digital tv receiver) and a small tv connected. With this setup, when I am working with my footpedal, it works for 1/2 an hour with proper play, rewind, and forward controls. After 1/2 an hour, it starts acting weird and begins to control itself in that it plays stops rewinds continuously by itself making it difficult for me. At first I thought it is driver issue and reinstalled and installed and tried all methods. I do get lot of errors at such times if I change the USB port for the pedal during the times of this issue. However, the moment I switch the DTH off from the power source. It all seemed to be working fine again without any issue.

Considering that, I thought it may be due to some voltage problem with distribution of power and I connected the DTH set seperately out to an entirely different AC wall socket but same room. Again, for the first half an hour the pedal controls works fine, and then the same thing happens and the moment I switch the DTH receiver off, its all back to normal.