Get some shades/window treatments
It's a must, unfortunately. Ideally whatever you end up with is of the room darkening type. Cheaper options would perhaps be bargain shades in combination w/ curtains (that include some degree of room darkening ability) from JCPenny or Target/Wal Mart.
The fast motion scenes can be problematic sometimes. Plasma handles such content better than LCD/LED. See if there's any sort of 'motion flow' (etc.) setting that can be toggled on/off.