Well, let's see if the ever fearful mods still have this IP banned….
Anyway - while stocks above a certain amount is hard to account for, the main issue is market liquidity. They are running out of liquid capital to settle/cover transactions. The stock clearinghouses are usually only required to cover a fraction of total stock value because rapid shifts of stock are rare. However, in this case, because these stocks have passed certain volatility markers, they have to cover in full and even 'just' a few billion dollars is enough to start freaking the clearing houses out because they don't have the capital to settle the claims.
So, if those volatile stocks keep raising, then the markets everywhere start to run out of liquid capital because it isn't usually held. A few million here, a few thousand there, and right back into the market it usually goes. Having a bunch of volatile investment all of a sudden is squeezing the liquid capital from the entire market.
So it seems to be an isolated issue, but it is spilling over into the whole market. If they start calling on commodities to bolster as liquid capital (gold or silver)… Oh boy will that be fun.