Tell me more about the form... what fields are you updating? What values did you set?
You may want to add some debug code right where the session variable is being set to see if it is at least trying to set it correctly.
Use:
Response.Write(Session("variablename"))
Response.End
to write the session variable right after it is created to see if it can be referenced immediately after it is set or if it is being set at all.