New players see hope in DSL market.

The promise of digital subscriber lines--a low-cost, high-speed Internet connection--was supposed to be the easy answer for small and mid-sized businesses looking to get wired. The reality, so far, has meant frustration among a growing number of DSL customers and hard times for several providers of the service in Massachusetts.

The difficulties seen in the local market, however, don't appear to have turned off demand for DSL service or the willingness to serve it up.

Qwest Communications International Inc. of Denver recently began offering DSL service to area businesses, and Marlborough-based Conversent Communications LLC this week got a significant boost in the form of an $81 million investment and a $105 million …