Switching to 144hz makes things choppy with dual monitor setup

[Friendly]

Just got a BenQ XL2411Z for 144hz in CS:GO and other games etc. I have my old Dell U2410 for watching Twitch / YouTube etc which runs at 60hz. I've noticed that video seems to get very choppy on both monitors when I turn the BenQ up to 144hz. My desktop is especially choppy on the BenQ monitor, borderline unusable. The mouse moves smooth as fuck though which is weird.

Current setup:

R9 280X
16GB DDR3 Corsair Vengeance
i5 2500k
Asrock Z77 Extreme 4

[editline]1st September 2014[/editline]

Just played a game of CS:GO which is absolute heaven and works perfectly. Still struggling with the desktop though.

[editline]1st September 2014[/editline]

Disconnecting the 60hz monitor resolves the choppy desktop issue, obviously not the solution I'm looking for though.

[editline]1st September 2014[/editline]

Somehow rebooting solved it. Oh well...