Do you have a mic plugged into your rig? If so, unplug it. Check Audio Hardware prefs to make sure they are set correctly, then give it another spin. Any improvement in performance?
Let us know, as that may help others solve this sticky issue.
Please also check your sequence settings and make sure the audio sample rate of your footage matches the sequence settings: i.e. 44.1K or 48K. That can help.
I went into audio hardware and set the Microphone option to 'No Input' and my video seems to be running smoothly now.
Weird fix, but a fix is a fix! Thank you!
Just a quick follow up, i was having this issue on my home computer (PC) as well as my work machine (Mac). Going into Audio Hardware is the preferences/settings and switching the "Default Input" to 'No Input' has fixed the laggy playback issue on both computers.