Have you done an upgrade recently? If so you may want to try recreating the OWA resource profile. I've occasionally ran into issues in the past where OWA SSO stopped working after an upgrade. What version of code are you running?
Hmm...your setup looks quite different than mine.
Under Autopolicy: Single Sign On (2nd attachment) I have the following:
Resource: http://my OWA server:80/owa/auth/logon.aspx?*
Post URL: http://my OWA server:80/owa/auth/owaauth.dll
Resource: (bottom entry in this field): http://my OWA server:80/owa/*
How are you authenticating OWA users directly: Basic auth (as you have configured) or form POST (as demonstrated by others on this thread)?