Flash plays too fast

I've seen this question multiple times across multiple forums, with no solutions in sight... so this calls for support.

What is wrong: flash video players embedded into webpages play video too fast with no sound, flash animations generally play too fast as well, with jerky motions.

Do I know when exactly this all started: no. No upgrades to hardware after which this glitch manifested, no OS overhauls, nothing. Periodic Microsoft updates is all I can think of.

OS version: WinXP 32 bit

Browser version: Chrome v. 24.0.1312.52 beta-m Firefox v. 17.0.1 IE v. 8

(problem manifests in Chrome and Firefox. IE is still able to play video with sound, but any attemp to browse to a different page when a video is playing causes the active tab to hang up)

Flash player version: 11.5.502.146

Fixes from Flash Player help (http://helpx.adobe.com/flash-player/kb/flash-player-games-video-or.html) I tried:

1. Deleted Flash Player browsing data

2. Removed Flash Player cache

3. Disabled hardware acceleration

None of this helped.

Also tried:

1. Fully removing the player, then installing it again.

2. Fully removing the player, then installing an older version.

3. Updating my graphics card drivers to the latest version.

4. Running my CPU at stock settings, no overclocking (this was actually listed somewhere as a possible solution).

No dice. The problem still persists.

It is, however, isolated to a single workstation - I have three more running the same OS version with the same updates installed (but with different hardware), and they do not have this problem.

Also, it is not isolated to a single website (like youtube) - for instance, animation that plays after installing the player on the corresponding page plays jerky, videos from www.escapistmagazine.com play on fast-forward etc.

What info should I get you to help me fix this problem?