An ongoing feud between the mayor of Richmond, Virginia and backers of a new performing arts center ratcheted up several notches this week when representatives of the PAC attempted to deliver a check for $2 million to the city. Under the terms of a 2004 agreement between the city and the PAC, the land on which the center is to be built will revert to city control in 2007 if a building permit is not secured by that time, unless the PAC chooses to pay the city $2 million. PAC officials decided to exercise that clause early, after months of wrangling with the mayor and other opponents of the project. But the mayor directed the city to refuse the check, and declared the entire 2004 agreement void, saying that PAC leaders were trying to buy the land well below market value.