It took more than 21 hours from the time polls closed Tuesday night for Fairfax County, the putative high-tech capital of the region, to get final election results from its new, computerized vote machines. Widespread problems in the system, which the county paid $3.5 million to install, also opened the door to possible election challenges by party leaders and candidates. School Board member Rita S. Thompson (R), who lost a close race to retain her at-large seat, said yesterday that the new computers might have taken votes from her. Voters in three precincts reported that when they attempted to vote...