The top after-market NYSE losers on Thursday are: LDK Solar Co, Hewlett-Packard, Aeropostale, Humana, GenOn Energy, First Commonwealth Financial and UBS AG.

LDK Solar Co. Ltd. (NYSE:LDK) shares slumped 21 percent to $5.19 in post market trading session as the company lowered its second quarter and fiscal 2011 revenue outlook.

For the second quarter, the company currently expects revenues to be in a range of $480 million to $500 million compared to its earlier estimation of $710 million to $760 million.

For fiscal 2011, the company revised its guidance for revenue to be in the range of $2.5 billion to $2.7 billion compared to its earlier estimation of $3.5 billion to $3.7 billion.

Hewlett-Packard Co. (NYSE:HPQ) shares declined 9.83 percent to $26.61 in aftermarket trading session. The company reported third quarter net income of $1.9 billion or $0.93 per share compared to $1.8 billion or $0.75 per share in the same quarter a year-ago. But that company issued a poor outlook for the full year, with revenues far below prior estimates of $129.1-billion.

The company also confirmed that it is negotiations to purchase Autonomy Corp. for about $10 billion and concurrently plans to spin off its personal-computer business.

Aeropostale Inc. (NYSE:ARO) shares declined 10.25 percent to $11.21 in post market trading session. Its second quarter net profit plunged to $2.9 million or $0.04 per share from $43.6 million or $0.46 per share in the same quarter a year-ago.

First Commonwealth Financial Corp. (NYSE:FCF) shares declined 4.14 percent to $10.56 in post market trading session.

Humana Inc. (NYSE:HUM) shares declined 2.9 percent to $69.95 in aftermarket trading session. The stock has a 52 week low of $47.21 and 52 week high of $84.32 and has $12.02 billion market capitalization.

GenOn Energy, Inc. (NYSE:GEN) shares declined 2.35 percent to $2.85 in post market trading session.

UBS AG (NYSE:UBS) shares declined 2.1 percent to $13.99 in aftermarket trading session. The company stock plunged more than 8 percent in regular trading session.

Nyse UBS AG Investment NYSE Euronext