Englewood, Colo.-based Rhythms, a provider of digital subscriber line service over ordinary phone lines, said that it and all of its wholly owned U.S. subsidiaries have voluntarily filed for Chapter 11 bankruptcy protection in New York. [...] Earlier this year, rival NorthPoint Communications, which had as many as 100,000 business customers, shut down its network, and sold its assets at fire-sale prices. Money-losing Covad Communications Group, which also was delisted from the Nasdaq national market and has been cutting jobs to pare costs in an effort to become profitable, said in May its auditors questioned its ability to remain in business.