noobie help

[wayne at taxupdate.com]

I'm trying to get started in understanding the gnucash sources (using v 1.8.9).
My learning project is an attempt to use guile to simply load a gnucash file:

(use-modules (gnucash app-utils))
(use-modules (g-wrapped gw-engine))
(use-modules (gnucash gnc-module))

(gnc:module-system-init)
(define session (gnc:session-new))
(gnc:session-begin session "/home/wayne/data/gnucash/Caliber" #t #f)
(gnc:session-load session)

Everything goes well until the last line, where I get:

Error: gnc_counter_end_handler: Unknown type: gnc:GncCustomer
Error: gnc_counter_end_handler: Unknown type: gnc:GncTaxTable
Error: gnc_counter_end_handler: Unknown type: gnc:GncBillTerm
  :
  :
  
Any suggestions on this?  On reference documents I should read?
 
Wayne