Flat file parsing in BTS2006 is pretty nice in general - you get a very specific error back in the error log if your incoming file is in the wrong format for the schema (or, put a more likely way, if you have buggered up creating the schema).
However, this vague error stumped us for a little while:
There was a failure executing the receive pipeline: "Orders.ContoFFPipeline.ContoFF, Orders.ContoFFPipeline, Version=1.0.0.0, Culture=neutral, PublicKeyToken=d5d6f7acdeb815af" Source: "Flat file disassembler" Receive Port: "RcvEnvelopedDocument" URI: "C:\FFIN\*.TXT" Reason: Unrecognized data in remaining stream
In our case this was due to a rogue carriage return at the end of the file (we had two instead of one!). Hope this saves someone some time!