Growing Gap Between Old Allies Creates New Obstacles for Haiti
Bitter dispute between two powerful factions in Haiti has broken apart American-backed ruling coalition and brought Government to virtual standstill, less than three years after US sent troops to restore democracy; rift between former Pres Jean-Bertrand Aristide and hand-picked successor, Rene Preval, has provoked economic and political instability; photo; Aristide has formally shifted allegiance to new party, Fanmi Lavalas, while many officials elected under his banner have remained in original Lavalas Political Organization, which backs Preval; Preval camp charges Aristide with fomenting violence that has killed more than 50 people; Parliament cannot muster quorum to approve laws to comply with international agreements; Aristide side charges Preval has sold out to US and IMF (M)