With a connection speed over 128Kbps, you should be able to use your computer to browse or do light internet activity while on a VoIP call.

Depending on your set up you may notice some quality loss if your computer is performing a heavy download or upload while you are on the phone. However this can be alleviated by utilising QoS (Quality of Service). QoS may not be helpful when a connection is being used heavily with applications such and Peer to Peer or torrents.