By Dan Gallagher, MarketWatch

SAN FRANCISCO (MarketWatch) -- The tech sector slumped by midday trades Thursday, weighed down by declines at Facebook Inc. and the company now known as BlackBerry despite an uplift from earnings rallies on stocks such as Qualcomm Inc.

The Nasdaq Composite (RIXF) was last down a fraction at 3,141 while the Philadelphia Semiconductor Index (SOX) slipped 0.2% and the Morgan Stanley High-Tech Index (MSH) also slipped by 0.2%.

Facebook (FB) slipped nearly 2% to $30.72 -- though was down as much as 6% earlier. Several brokers downgraded the stock following the social network's fourth-quarter results, which included a forecast for heavy spending in 2013.

"With our earnings model totally recalibrating, it is time to take some profits and evaluate the likelihood of potential earnings upside in future quarters," Jordan Rohan of Stifel Nicolaus wrote as he cut his rating on the social network to hold from buy, leaving his $31 price target intact.

BlackBerry, which still trades under the name Research In Motion (RIMM) , slid nearly 5% to $12.76. Credit Suisse downgraded the stock to underperform, a day after the company unveiled a new line of smartphones for its BlackBerry 10 operating system that will launch next month.

"Despite recent enthusiasm for RIM's new BB10 devices, we see limited scope for traction in the hypercompetitive smartphone market," wrote Kulbinder Garcha of Credit Suisse in a note to clients.

Shares of Take-Two Interactive Software (TTWO) fell nearly 7% to $12.16 after the company announced that it will release "Grand Theft Auto V" on Sept. 17. The launch of the highly anticipated sequel to the best-selling urban action franchise comes later in the year than the original planned spring release, "in order to allow additional development time," the company said in a statement. The title will be available for the Xbox 360 and PlayStation 3 consoles.

GameStop (GME) shares slid more than 3% on the news. Publisher Electronic Arts (EA) moved up nearly 3%. The later release of GTAV may put the title against greater competition in the busy holiday selling season.

Fusion-io Inc. (FIO) fell more than 16% after its own quarterly report that included a downbeat forecast that the company blamed on slowing orders from major customers such as Apple (AAPL) and Facebook. At least three brokers downgraded the stock following the results.

Qualcomm (QCOM) shares jumped nearly 5% after the maker of wireless device chips delivered better-than-expected results and a positive forecast. Several analysts raised their price targets on the stock following the report.

Citrix Systems (CTXS) jumped more than 10% after the enterprise software maker reported a gain in earnings and issued a forecast that beat Wall Street's expectations. The stock was upgraded to a buy rating at Bank of America/Merrill Lynch.

JDS Uniphase (JDSUD) shares jumped more than 16% following the company's results, which topped Wall Street's projections. Needham & Co. upgraded the stock to a buy rating.

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