Did anyone ever resolve this?  I am having the exact same issue...returning
results from a FOR XML procedure to an ado stream object stops working every
several days.

I have this function that worked like a charm under IIS5 and W2K.  You pass a
sql string that has for xml auto or a stored produre that has for xml auto in
it.  Under IIS6 and W2K3 it stops working after a couple of days with no
rhyme or reason.  No error log either.  We applied all the service packs
including sqlxml sp3.  What is wrong? Thanks.

Here is the code:
function getSQLXML(byval sqlString)
    dim adoConn
    dim adoCmd
    dim adoStreamQuery
    set adoConn = vbsqlconnection 'located in sharedfunctions.asp
    adoConn.CommandTimeout = 300
   
    set adoStreamQuery = Server.CreateObject("ADODB.Stream")
    set adoCmd = Server.CreateObject("ADODB.Command")'
    adoCmd.ActiveConnection = adoConn
    adoCmd.CommandTimeout = 300
    adoConn.CursorLocation =  adUseClient

    dim sQuery  
    sQuery = "<recordset xmlns:sql='urn:schemas-microsoft-com:xml-sql'>"
    sQuery = sQuery + "<sql:query>"+sqlString+"</sql:query>"
    sQuery = sQuery + "</recordset>"
               
    adoStreamQuery.Open    'Open the command stream so it may be written to
    adoStreamQuery.WriteText sQuery, adWriteChar   'Set the input command
stream's text with the query string
    adoStreamQuery.Position = 0   'Reset the position in the stream, otherwise
it will be at EOS

    adoCmd.Dialect = "{5D531CB2-E6Ed-11D2-B252-00C04F681B71}"   'Set the
dialect for the command stream to be a SQL query.
    adoCmd.CommandStream = adoStreamQuery     'Set the command object's command
to the input stream set above

    dim outStrm
    set outStrm = Server.CreateObject("ADODB.Stream")     'Create the output
stream
    outStrm.Open

    adoCmd.Properties("Output Stream").Value = outStrm  'Set command's output
stream to the output stream just opened    
    adoCmd.Execute , , adExecuteStream
    'Response.Write(outStrm.ReadText)
    adoCmd.ActiveConnection = nothing
    adoConn.Close
    set adoConn = nothing
    getSQLXML = outStrm.ReadText
end function

P.S. Goorbeeman in the group microsoft.public.sqlserver.server has the same
problem