Nasdaq OMX (NASDAQ:NDAQ) suffered a glitch Friday morning that left its markets stuck in neutral for nearly an hour, bringing back memories of last year's "Flash Crash" that rocked investor confidence.

The outage, which is being investigated by Nasdaq, meant that investors around the world were unable to receive a reading on the Nasdaq Composite and other major indexes. Despite the opening bell having been rung, the Nasdaq Composite was indicated as unchanged until just before 10:30 a.m. ET. 

To clear up the confusion, Nasdaq began disseminating several of its indexes from its back-up calculator. Bullish traders may have preferred the unchanged reading as the Nasdaq Composite quickly plunged 1.2%. 

It's not clear what caused the glitch, but Nasdaq said it was investigating an outage on the Global Index Data Service that is impacting the dissemination of its indexes. 

The outage caused confusion as individual stocks that trade on Nasdaq such as Apple (NASDAQ:AAPL) and (NASDAQ:AMZN) showed what appeared to be normal trading, but the Nasdaq Composite was unchanged at the previous day's close of 2755.28. 

Nasdaq OMX's stock retreated amid the confusion, slumping 1.94% to $24.73. Nasdaq did not immediately respond to a request for comment from FOX Business. 

Friday's incident likely reminded investors of the chaos caused by last May's "Flash Crash," which caused the Dow Jones Industrial Average to briefly plummet nearly 1,000 points before recovering. It marked the benchmark index's worst point drop on record and weighed heavily on market sentiment.

“It’s clearly not going to increase investor confidence,” Michael James, managing director of equity trading at Wedbush Securities, said of Friday's glitch.

While the Dow gets much of the attention, the Nasdaq Stock Market is the largest electronics screen-based equities trading exchange in the U.S. From a market value standpoint, Nasdaq OMX is the No. 2 operator in the world behind rival NYSE Euronext (NYSE:NYX).

Known for its largest allotment of technology stocks, the Nasdaq Composite lists more than 3,000 companies, including Google (NASDAQ:GOOG), Oracle (NASDAQ:ORCL) and FOX Business parent News Corp. (NASDAQ:NWSA).