Monday's Winners & Losers: MBIA

MBIA(MBI Quote) shares continued to plummet after the company on late Friday disclosed how it planned to respond to recent ratings agency downgrades. The bond insurer said it will require $2.9 billion to satisfy potential termination payments and expects to be required to post roughly $4.5 billion in eligible collateral to satisfy potential collateral posting requirements. The stock swooned 13.8% to $4.82 on Monday, as shares of its chief competitor, Ambac(ABK Quote), also descended 6.3% to $1.92.

The Wall Street Journal reported Citigroup(C Quote) was readying pink slips for 10% of its work force, as the banking giant attempts to recover from bad mortgage investments. Shares of Citi were giving back 3.4% to $18.64.

Handset maker Motorola(MOT Quote) was down 49 cents, or 6.2%, to $7.45 after T. Michael Walkley, an analyst at Piper Jaffray, cut his rating on the stock to sell from neutral and reduced the price target to $7 from $9.75. Motorola continues to lose market share in North America, which represents nearly half of the company's unit sales, Walker said.

Satellite radio maker Sirius(SIRI Quote) continued to trade lower as investors remained concerned about its $4.6 billion acquisition of rival XM Satellite Radio(XMSR Quote).

Nearly a year and a half later, Sirius is still waiting for the deal to close, even as last week a Goldman Sachs analyst slashed his price target on the two stocks. Shares of Sirius were down 6 cents, or 3%, to $1.93, while XM shed 20 cents, or 2.4%, to $8.10.

Barrier Therapeutics (BTRX Quote) jumped 129%, or $2.27, to $4.03 after the company announced it will be bought out by private company Stiefel Laboratories in a deal worth roughly $148 million. Stiefel is paying $4.15 a share in cash, a 73% premium to Barrier's average closing price for the last 30 days. The companies expect the deal will close by the end of the third quarter.