Recently I got the following error while trying to write out a flat file. The way I resolved it was to remove the .dll from the GAC and resinstall the .msi.

Event Type: Error
Event Source: XLANG/s
Event Category: None
Event ID: 10025
Date: 4/28/2009
Time: 12:01:17 PM
User: N/A
Computer: YOURCOMPUTER

Description:
Uncaught exception (see the ‘inner exception’ below) has suspended an instance of service YOURPROCESSNAME’.
The service instance will remain suspended until administratively resumed or terminated.
If resumed the instance will continue from its last persisted state and may re-throw the same unexpected exception.
InstanceId: 3f85458e-35c0-4f56-bce9-c4dc7a054f5f
Shape name: Send msg_FlatFile
ShapeId: 65a1739e-9b12-41c2-abb1-1aa2776d2657
Exception thrown from: segment 1, progress 22
Inner exception: Failed while attempting to send message ‘msg_FlatFile’.
Exception type: SendFailedException
Source: Microsoft.XLANGs.BizTalk.Engine
Target Site: Void WriteMessageState(Microsoft.BizTalk.Interop.IBTPEPInfoLookup, System.Guid, Microsoft.XLANGs.BaseTypes.XLANGMessage, Microsoft.XLANGs.Core.Segment, System.String, System.String, System.Collections.IList, Boolean, System.Collections.IList)
The following is a stack trace that identifies the location where the exception occured

at Microsoft.BizTalk.XLANGs.BTXEngine.BTXXlangStore.WriteMessageState(IBTPEPInfoLookup pepLookup, Guid portId, XLANGMessage msg, Segment seg, String opname, String url, IList promoteProps, Boolean track, IList toPromote)
at Microsoft.BizTalk.XLANGs.BTXEngine.BTXLogicalPortBinding.SendMessage(XLANGMessage msg, XlangStore store, Segment seg, OperationInfo op, IList additionalProps, IList toPromote, Boolean ignoreRoutingFailure)
at Microsoft.BizTalk.XLANGs.BTXEngine.BTXPortBase.SendMessage(Int32 iOperation, XLANGMessage msg, Correlation[] initCorrelations, Correlation[] followCorrelations, Context cxt, Segment seg, ActivityFlags flags)
at YOURORCH.segment1(StopConditions stopOn)
at Microsoft.XLANGs.Core.SegmentScheduler.RunASegment(Segment s, StopConditions stopCond, Exception& exp)
Additional error information:

Exception from HRESULT: 0xC0C01672
Exception type: COMException
Source: Microsoft.XLANGs.BizTalk.Engine
Target Site: Void PostToSendPort(System.Guid ByRef, Microsoft.BizTalk.Agent.Interop.IBTMessageBatch, Microsoft.BizTalk.Agent.Interop.IBTMessage, System.String, System.String, Microsoft.BizTalk.Interop.IBTMMessageList ByRef)
The following is a stack trace that identifies the location where the exception occured

at Microsoft.BizTalk.Interop.IBTPEPInfoLookup.PostToSendPort(Guid& sendPortID, IBTMessageBatch batch, IBTMessage msg, String operationName, String url, IBTMMessageList& dlMsgList)
at Microsoft.BizTalk.XLANGs.BTXEngine.BTXXlangStore.WriteMessageState(IBTPEPInfoLookup pepLookup, Guid portId, XLANGMessage msg, Segment seg, String opname, String url, IList promoteProps, Boolean track, IList toPromote)

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