As traders await the 3:25 PM ET full reopening of the Nasdaq, the anticipation is that the picture isn't going to be pretty.
A problem that began at the Nasdaq spread through the trading world and has market pros on edge for what is next.
"I've never seen anything like this in my life," said Dave Rovelli, managing director of U.S. equity trading at Canaccord Genuity. "It's horrible."
Once trading gets the OK to start again, traders will get a five-minute grace period in which they can submit quotes, trade imbalances and conduct other business matters.
Dozens of publicly traded companies, including high-profile companies such as Apple, Microsoft and Facebook, were showing their shares halted. The Nasdaq status message was time stamped at 12:14:03 ET.
When it re-opens, things could get interesting.
A spike in volume will be likely, particularly from computerized trading programs that aren't set up to handle a lengthy shutdown from a major global exchange.
"You will have some pent-up activity," said Dave Lutz, managing director of trading at Stifel Nicolaus. "Algos are going to try to make up for an hour and a half you missed, which could seriously skew an illiquid security."
The effects will not be universal.
At some desks, Lutz said, the problems at the Nasdaq were barely noticed.
"We're calling all our customers. They're updated with what the Nasdaq is intending to do," he said. "You have to make sure your customers are not caught with their pants down once they start trading again."
The delay was yet another black eye for a market that has suffered through flash crashes, embarrassing glitches in initial public offerings and a general perception of being an uneven playground.
"All you should do is watch the Nasdaq stock, the NDAQ. They'll probably hit the stock like they did after the Facebook debacle," Rovelli said.
The problems prohibited "a single share" from trading in any of the Nasdaq stocks, though others exchanges remained open.
"Everything is on lockdown," Rovelli said. "For a little while you could trade in dark pools, but even my dark-pool vendor shut down."
Another trader said "the last time this happened, a squirrel chewed through a wire."
However, Thursday's shutdown appeared more serious.
It marked yet another embarrassment for mass trading platforms and the Nasdaq in particular.
The exchange suffered a previous setback in May 2012 when the much-ballyhooed initial public offering for Facebook was delayed about half an hour due to technical problems.
_ By CNBC's Jeff Cox. Follow him
@JeffCoxCNBCcom on Twitter.