>I've been through this type of situation in the past too. Any idea why manually trying to set the Datasession causes such, er, fun?

No. Do you reset it properly? How do you do it? Try:

(NOT TESTED CODE:)

local lnDS, loSession
lnDS = thisform.datasessionID
loSession = createobject('session')
thisform.datasessionID = loSession.DataSessionID

..... &&Bunch of code

thisform.datasessionID = lnDS
loSession = .NULL.