A bit more info here, and I dont know if I am barking up the wrong tree.
If I add this line
Session("var_auctionid") = WA_AppBuilderRecordset.Fields.Item(WA_indexField).Value
AFTER this one
if (NOT WA_AppBuilderRecordset.EOF) then Session(WA_sessionName) = WA_AppBuilderRecordset.Fields.Item(WA_indexField).Value
Which in theory is doing the same thing, but without using the WA function variables and excluding the "If NOT" statement then I get this error:
ADODB.Field error '800a0bcd'
Either BOF or EOF is True, or the current record has been deleted. Requested operation requires a current record.
/members/additem.asp, line 55
Which suggests the the extension is not picking up the newly inserted record - which does exist by the way because I checked the SQL table and also the ID field is definately an autonumber.