Dell Inspiron 5520 Switchable Graphics Problem

Hello,

Whenever I try and run certain games on high performance mode (with AMD Switchable Graphics), with a monitor plugged in, and set to extend desktop, both the laptop and monitor screens just rapidly flash black, and nothing happens for a while. Trying to run the game in power saving on Switchable graphics works fine. Running the game in high performance, with windows set to use the monitor only works fine, and same with laptop screen only. Therefore it is only an error when using BOTH at the same time. However, only certain games (Direct X I think, but could be wrong) do this, whereas others work flawlessly on high performance, with both monitors.

Any help would be appreciated,

Thanks,

Dylan.