SQL Server 2008: MERGE command on a table that has a trigger causes an error

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SQL-Server

I have a stored procedure that uses the MERGE command to synchronize dbo.tableA with [mylinkedserver].dbo.TableA.

TableA has an insert/update trigger associated with it. To keep things really simple all the trigger does is

print 'I am a simple trigger because i dont want to cause errors'

When the SP is executed (thru a .net windows application), it throws this error:

OLE DB provider "SQLNCLI10" for linked server "MyLinkedServer" returned message "No transaction is active."

If I delete the trigger and execute the stored proc again, it executes absolutely fine.

The stored procedure also runs fine (with the trigger) if i run it through SSMS.

MSDTC is enabled on both servers.

Server is Windows 2008 server, SQL Server 2008 with service pack 2.

Why would a trigger cause this error ?!?!??