Used to get this in X3 but in Platinum last night I performed the following action:
 
Drag a rex wav file onto track. 
Bounced to clip
Ctrl dragged to 50% length, therefore time stretching it. Press play... MASSIVE OUCH AND IMMEDIATE DEAFNESS! - which by the way was painful as I already have tinnitus.
As in this post's title, there was an almighty cacophony of glitchy feedback sound that was cured by clicking the reset audio button.
Bounced the offending 50% stretched audio to a clip and all was well again.
 
Anyone got any suggestions as to how I can protect my hearing from this glitch? Has happened a few times in Platinum (very latest version) and it's always related to audio clips and time stretching.

To eliminate the problem at the source, try disabling 64-bit Double Precision Engine in preferences. I've had something like the problem you describe when stretching audio with 64-bit DP enabled.
 
To guard against high-level audio glitches, you can put any limiter plugin on the last bus before your main outs (preferably something with minimal latency like Concrete Limiter); I believe there are also 3rd-party plugins that are intended for this purpose. I often have a bus called "> Main Outs" after the Master for other purposes that would lend itself to this. When exporting, use Source = Master bus instead of Main Outs or Entire Mix to avoid having that bus affect the finished product.
 
All that said, if you have your monitoring system output level and project gain-staging set appropriately, even a continuous 0DB signal should not be painful, though 'surprising' your ears with a high-level transient when they are attuned to a lower level signal can still be unpleasant.

You must have (well) powered monitors.
 
Get a monitor controller like this one that I have for my 150 watt mackie hr 824s.
That way unintended full blast audio from your daw will not be nearly as full blast.