issue with open apps

[Mr.Noisy]

for some reason, ive noticed since yesterday that i can only have 1 app open in a window at a time, i sometimes play a film whilst surfing the net for example, but now if ive got safari open ,then i play a film the dvd player or quicktime will open and safari disappears, it's still open but not showing?, if i check spaces it's not showing there either??
please any advice/help greatly appreciated before the inevitable re-install of os, tar

safari,mail and quicktime open in space 1, but this is all i get using grab, but it should show open apps in the windows, example below of spaces and the dock with apps that are open:

 

[Mr.Noisy]

issue resolved

My son just got a lifetime ban from the mac pro, he can stick to using his mbp forever, he had been playing with macpilot, and enabled single application mode, simple fix after interrogation techniques were applied, a bit of patience and the threat of violence, always works .