I believe Asio4ALL don't like sharing Apps.
This below may help. Some folks seem to have similar problems.
Playback of Reaper and other applications simultaneously
External Audio devices (PC's, using ASIO drivers) are always worth investigating, especially for the price you can get them at these days. In the end, they save you a lot of grief.
Sorry, I know it's not what you want to hear at the moment.