Defined pension benefit plans run by major Connecticut companies suffered significant investment losses this year, pushing several plans into the red and further eroding plans that were already in negative territory. Companies like Praxair and Phoenix Cos. had pension fund liabilities greater than assets at the end of 2007, before their stock-heavy portfolios were battered by the downturn. Although a 2006 law required companies to make up deficits quickly, corporate lobbying to ease the rules in light of the general crisis appears to have paid off.