Xilinx ( XLNX) rose 12.5%, a day after the company posted third-quarter earnings that beat analysts' expectations. On Friday, Citibank noted that the programmable logic chipmaker wasn't experiencing macroeconomic weakness. Xilinx shares were up $2.39 to $21.53. MBIA ( MBI) shares got kicked even lower after the bond insurer announced that Moody's is mulling a cut of its vital triple-A insurance financial-strength rating, as well as those of its insurance affiliates. Also on review for possible downgrade, among other things, are the Aa2 ratings of the surplus bonds MBIA just issued last week in an effort to shore up its worrisome capital levels. MBIA is baffled by the move, saying Moody's had asked for a solid cash position last month and that MBIA had responded in kind -- via the bonds, a dividend cut, and an earlier cash injection agreement for up to $1 billion from Warburg Pincus. And the bonds' Aa2 rating, it groused, was just assigned last week. Plus, it added, both Fitch Ratings and Standard & Poor's have recently affirmed their top-notch ratings of MBIA. MBIA shares were sliding another $1.15, or 12.5%, to $8.07 following a very tough couple of days which saw rampant selling by nervy investors as they observed the varied travails of MBIA rival Ambac ( ABK), including a vacating CEO. The most damage came yesterday when Moody's said it would rethink Ambac's Aaa rating . Shares of Level 3 Communications ( LVLT) slipped as the daytrading favorite continued to dance around the $3 level. The stock has been below $4 for the past three months. Shares were recently off 22 cents, or 7.2%, to $2.84. Shares of Amcol ( ACO) retreated 15.5% to $26.18 on fourth-quarter earnings. The Arlington Heights, Ill., minerals company posted income of $10.8 million, or 35 cents a share, vs. $12 million, or 39 cents a share, in the year-ago quarter, falling short of analysts' mean forecast of 44 cents a share. Among the day's winners, Performance Food Group ( PFGC), a Richmond, Va.-based marketer and distributor of brand food and nonfood products, saw shares jump 31% to $31.72 on news that an affiliate of Blackstone Group ( BX) would buy the company for about $1.3 billion, or $34.50 a share, in cash. Meanwhile, UBS ( UBS) shares fell 4.3% after the Financial Times reported that the Swiss bank intends to let go of half the employees in its real estate and securitization businesses amid a larger shakeup of its investment banking unit, per an internal memo from CEO Marcel Rohner.