Shares of Alon USA Energy ( ALJ) slipped after the Dallas-based petroleum products company said it received notice from Plains Pipeline and another owner of the Mesa Pipeline System that a dispute has arisen regarding the continued operation of the line. According to the notices, Plains and another owner believe the Mesa system should be discontinued July 1. A third owner wants to keep the system open. The Mesa Pipeline System supplies more than 90% of the crude oil refined by Alon's refinery in Big Spring, Texas. Although Plains and one of the other owners of the Mesa System have offered alternatives to supply crude oil to the Big Spring Refinery, Alon has started implementing contingency plans. Shares of Alon fell 36 cents, or 1.6%, to $22.55 in recent trading. Vail Resorts ( MTN - Get Report) dropped after the Vail, Colo., resort company said Chairman and CEO Adam Aron will resign effective June 28 after 10 years in the posts. The company said it will begin an immediate search for a successor. Shares of Vail Resorts slid 70 cents, or 2.2%, to $31.77. Shares of W-H Energy Services advanced after the Houston oilfield-services company said its fourth-quarter net income rose to $16.2 million, or 55 a share, from $7.5 million, or 26 cents a share, a year ago. Analysts polled by Thomson First Call expected the company to earn 47 cents a share. Revenue climbed 32% to $173.3 million. The company projects that earnings will range from 54 cents to 58 cents a share for the first quarter. Analysts are calling for earnings of 51 cents a share. W-H Energy Services gained $3.92, or 9.3%, to $46.22 in recent trading. WorldSpace rose after the Silver Spring, Md.. satellite-based digital radio company said it signed new lockup agreements through Dec. 31 with certain managers, including its CEO. The agreement also covers certain shares held by its directors and other significant stockholders. The new lockup agreements apply to 34.1 million common shares. WorldSpace gained 56 cents, or 4.4%, to $13.24. Shares of Intrado added more than 11% after the Longmont, Colo., communications company said it was being acquired by West Corp. ( WSTC) for $26 a share in cash, or about $465 million. Intrado advanced $2.63 to $25.63 in recent trading.