Dear Matt,
there are traces in ABAP directly for SPNego.
See http://help.sap.com/download/sapsso/secure_login_impl_guide_en.pdf chapter 4.5.5.5.
1. Start SPNego Configuration (transaction SPNEGO)
2. Choose Goto SPNego Tracing .
Related Information:
SAP note 1732610
SAP note 1819808
best regards
Alexander Gimbel