NEW YORK (CNN/Money) - Credit Suisse First Boston raised its investment rating on rail operator CSX ahead of the opening bell Tuesday, while DB Securities increased its price objective for AOL Time Warner.

Credit Suisse First Boston upgraded CSX (CSX: Research, Estimates) to "outperform" from "neutral," saying the company is underearning its potential. Shares of CSX fell 63 cents to $30.89 Monday.

Merrill Lynch cut its investment rating from on AK Steel (AKS: Research, Estimates) to "neutral" from "buy," citing an outlook for continued losses based on upwards cost pressures and continued weak demand. AK Steel slipped 19 cents to $2.45 Monday.

Merrill upgraded Argosy Gaming (AGY: Research, Estimates) to "buy," saying the worst is behind the company. The casino operator fell 11 cents to $20.13 in trading Monday.

DB Securities cut its rating on Lexmark International (LXK: Research, Estimates) to "hold" from "buy" in a research note dated July 21. Shares of the printer maker sank $14.10 to $59.40 Monday, when the company posted disappointing quarterly results.

DB Securities also raised its 12-month price target on AOL Time Warner (AOL: Research, Estimates), parent company of CNN/Money, to $21 from $19. The media conglomerate dropped 39 cents to $16.35 Monday.

Lehman Brothers downgraded Dime Community Bancshares (DCOM: Research, Estimates) to "equal weight" from "overweight." Shares of the financial services company fell a penny to $26.62 Monday.

Lehman upgraded Novellus Systems (NVLS: Research, Estimates) to "overweight" from "equal weight" after the company posted quarterly results that came in-line with expectations. Shares of the maker of microchip production equipment slid $1.55 to $34.55 Monday.

Lehman also raised its investment rating on Applied Materials (AMAT: Research, Estimates) to "overweight" from "equal weight." Shares of the chip equipment maker fell 31 cents to 17.87 Monday.

Goldman Sachs cut its 2003 profit estimate for Israel's Check Point Software Technologies (CHKP: Research, Estimates), a day after the Internet security company posted in-line second quarter results, saying license revenue was disappointing and that the company is not attracting new customers. Check Point slid $2.67 to $17.13 Monday.  

-- from staff and wire reports