Acxiom (ACXM) shares plummeted 19.7%, after it reached an agreement with two private equity firms to end a previously announced $2.25 billion buyout. Silver Lake and ValueAct Partners will pay $65 million in cash to the data management company as a break-up fee. Acxiom shares were falling $3.90 to $15.89.

Radvision (RVSN) were down over 17.4% after the company lowered its third-quarter revenue forecast. The company now expects revenue of $20.5 million, compared with its previous projection of $25 million. Analysts anticipated revenue of $25.1 million, according to Thomson Financial. Radvision, which makes products for videoconferencing, video telephony and the development of voice-over-Internet protocol systems, said the decline is due to lower-than-expected sales both to the federal market and through its channels. Shares were falling $3.06 to $14.50.

SXC Health Solutions (SXCI), an information-technology purveyor for the health-care industry, sliced at least 8 cents off its fiscal 2007 profit forecast to between 51 cents and 55 cents a share. The Lisle, Ill., company also trimmed its revenue guidance down to between $92 million and $93 million. Analysts polled by Thomson Financial are seeking revenue of $96 million. Shares lost $2.97, or 18.5%, to $13.05.

Par Pharmaceutical (PRX) traded down after a Friedman Billings Ramsey analyst downgraded shares on Monday, saying the generic drug maker will not recover from declining sales until 2009. On Friday, Par gave an annual forecast that fell far short of analyst estimates, and the stock dropped 14.4 percent, reaching a year low. The company said sales have been weak due to difficult competition, which will lead to weaker revenue and less profit for the year.

EFJ Inc. (EFJI) said Tuesday it will post a "significant operating loss" for the third quarter and lowered its revenue forecast for the full year, sending shares tumbling more than 30 percent in midday trading. EFJ cited a more rapid-than-expected market decline of its Transcrypt products, a delay in revenue from its secured communications 3eTI business, and higher-than-expected costs in its EFJohnson business. Quarterly revenue is now expected to range between $32 million and $33.5 million. For the full year, the company now expects to report anywhere from a loss of $2 million to income of $1 million, compared with earlier projections for operating income of $7 million to $10 million. Revenue is now seen between $160 million and $170 million, well below prior estimates of $185 million to $195 million. (AP)

Usec (USU) were dropping 5%, after a bid with Energy Solutions to clean up uranium-enrichment plants was rejected by the U.S. Energy Department. It was the largest drop in over seven years, according to Bloomberg. Shares were falling down 51 cents to $9.64.

Aventine Renewable Energy Holdings Inc. (AVR) dropped when ethanol stocks continued their downward trend on Tuesday, as companies discussed the industry's weak outlook at an investors conference. Aventine fell hardest, with a decline of 93 cents, or 8.7 percent, to close at $9.75. Aventine's shares have dropped about 60 percent since the start of this year.

Rite Aid (RAD) operates a chain of retail drugstores. It has been downgraded to a sell from a hold. The ratings change is driven by a few notable weaknesses, which TheStreet.com Ratings believe will have a greater impact than any strengths. The company's losses widened in the second quarter to 10 cents per share from two cents per share a year earlier. Net losses also widened to $69.90 million from $330,000. Rite Aid's debt-to-equity ratio of 2.08 is higher than the industry average, implying that there is very poor management of debt levels. In addition, the company's quick ratio of 0.35 demonstrates the inability to cover short-term cash needs. Rite Aid had been rated a hold since September 2005. The stock hit a 52-week low.