Flash Ads Lag When Loading and On Mouseover

Windows Vista SP2 x64

Firefox 22.0, also hangs in Chrome 27.0 & ie 9 x64

Flash 11.7 and 10.3 both tested with no change

All addons disabled except for Flash.

Very noticeable hang (more with certain ads) when loading an ad on justin.tv or twitch.tv.  The hang can last up to 15 seconds, where the browser will not respond.  The ads/browser also lag when I mouse over the ads.  I believe this also happens on youtube, but is more rare.

The audio does not lag after the initial load/hang.  Rolling my mouse over the ad and continuing to move the cursor creates significant video lag/frame dropping during ad playback.  This does not continue noticeably during normal video.

My current workaround is to run adblock in Chrome, but I'd much rather support content creators by running their ads.

This has been happening for approximately a year now, I've tried uninstalling/reinstalling flash, upgrading to latest versions, wiping all cached files, and using other browsers.

It looks like I have enough bandwidth to run 6-ish streams at 240p simultaneously and smoothly, and I've never had an issue with running a stream @ 1080p.  With an ad, though, the ad runs at a drastically reduced framerate, making the experience unbearable.

EDIT: Have tried enabling/disabling hardware acceleration in both Firefox and Flash settings to no effect

EDIT2: There seems to be a massive CPU usage spike during the load and ad playback, from only 5% usage during normal stream viewing up to 30%-40% during the ad load->playback+mouseover (Viewed in Task Manager)

EDIT3: Also happens in ie x64