Please Check your system Settings.
Open Power Settings under Control Panel -> All Control Panel Items -> Power Options.
Click "Change plan settings".
You'll find "Change advanced power settings".
Search for "Switchable Dynamic Graphics" in the "Power Options" dialog and change the "Global Settings", "On battery" and "Plugged in" to "Maximize performance"
Now both, HeavyLoad and other programs which have the same problem should work again.
Also make sure you have the latest drivers installed for your graphics cards.