Tuesday's Winners & Losers: Assured Guaranty

Kick-starting a hopeful rally this morning was Warren Buffett, who told CNBC that he has already offered to pump lifeblood back into struggling bond insurers Ambac (ABK Quote), MBIA (MBI Quote), and Financial Guaranty Insurance, by reinsuring $800 million in municipal bonds for which the firms are currently responsible.

Regardless, Ambac and MBIA themselves were sliding -- by 13.2% to $9.10 and 11.5% to $12.02, respectively -- after the proposal got a lukewarm reception. Buffett, whose Berkshire-Hathaway (BRK.A Quote) launched a bond insurance firm of its own in December, said that one of the firms has already rejected the offer while the other two haven't yet responded.

Shares of Nuance Communications(NUAN Quote) jumped a day after the company beat first-quarter earnings estimates and guided revenue higher for the second quarter. In a research note Wednesday, Friedman Billings said it appears the company is continuing to see a healthy spending environment across all core speech segments, as demand for speech technology is disproportionably benefiting Nuance in the field. Nuance rose $1.94, or 11.9%, to $18.19.

GMH Communities (GCT Quote), a real estate investment trust based in Newtown Square, Pa., rose 55.5% to $8.69 on news that American Campus Communities (ACC Quote) would buy GMH for $1.4 billion in cash and stock. American Campus shares, meanwhile, fell 1.5% to $28.

Bermuda life-insurance company Assured Guaranty (AGO Quote) saw its fourth-quarter operating income dip by 3 cents from a year ago to 53 cents a share, but that was 2 cents ahead of expectations. And, also in that quarter, St. Louis brokerage Stifel Financial (SF Quote) came in far ahead with a rising non-GAAP profit of $20.5 million, or $1.14 a share. Assured rose 7.2% while Stifel spiked 12.3%.

Shares of Nvidia(NVDA Quote) rose ahead of its earnings report after the closing bell on Wednesday. A report by Kaufman said the firm believes Nvidia has been able to hold the line on pricing and will continue to drive cost and mix improvements to hold or even improve margins in the next few quarters. Nvidia was up 93 cents, or 3.7%, to $26.00.

Not all stocks performed as valiantly. Dycom Industries (DY Quote) last night lowered its outlook for its second quarter of fiscal 2008. The contractor now expects non-GAAP earnings to range from 3 cents to 4 cents a share, which is 11 cents to 12 cents below the low end of its November 2007 guidance. Analysts are looking for 20 cents a share. Friedman Billings brought more pain by downgrading Dycom to market perform from outperform this morning. The Palm Beach Gardens, Fla.-based company saw shares retreat 31.4% to $15.99.