MSDTC(Transaction problem)

Question

Dear All,
I have an .net 2.0 application hosted on a server,and data base on a different server.In my .net code i have used system.transactions,when i execute that code,one connection is opened successfully,when i try to open another connection in same transaction block,an exception "Communication with the underlying transaction manager has failed".I have done following till now,but all in vain.
1.Enabled DTC service on both servers(web and db)
2.Check all check boxes in DTC services(component services->DTC properties)
3.Allow of port 134,135 and 5500-5700 on both server
4.Add an exception in the firewall of these ports
5.Enabled RPC service,and done required settings in regedit for rpc
6.Tried disabling firewall,but that also didn't work