ManTech

Ticker: MANT

Friday's close: $13.64

Week's change: -16%

ManTech's stock dropped after the Fairfax high-tech defense contractor said new government policies will hurt its personnel security-investigation business. As a result, ManTech said, it expects next month to report a loss for the second quarter.

Black & Decker

Ticker: BDK

Friday's close: $67.21

Week's change: +11.4%

Shares of Black & Decker rose sharply last week after it reported strong second-quarter earnings and sales. The Towson toolmaker earned $121.6 million compared with $75.7 million a year ago. The company also said it would buy the tool division of Minnesota-based Pentair Inc. for $775 million.

Nextel Communications

Ticker: NXTL

Friday's close: $23.59

Week's change: -8.5%

The Reston-based cell phone company's earnings soared to $1.3 billion in the second quarter from $281 million. But analysts said investors are worried about increased marketing costs and the costs of a plan to eliminate interference between Nextel's phones and public safety communication systems.

CoStar

Ticker: CSGP

Friday's close: $43.25

Week's change: +8.9%

CoStar's shares jumped after the Bethesda real estate information firm reported it swung to a profit of $1.7 million in the second quarter compared with a loss of $367,000 a year ago. CoStar also announced it had won a defamation lawsuit in California.