I just experienced the blackout to login screen again while right in the middle of working so I opened up system.log and copied this out. Not sure if someone is able to see anything useful from it, but I thought I would share:
MacBook-Air kernel[0]: AppleCamIn::handleWakeEvent_gated
MacBook-Air kernel[0]: AppleCamIn::acpiControlS2ChipPower - powerState=0, status = 0x0, result_value = 0x0
MacBook-Air.local airportd[2111]: _doAutoJoin: Already associated to “JG 5GHz”. Bailing on auto-join.
MacBook-Air.local loginwindow[56]: in pam_sm_authenticate(): Got user: ben
MacBook-Air.local loginwindow[56]: in pam_sm_authenticate(): Got ruser: ben
MacBook-Air.local loginwindow[56]: in pam_sm_authenticate(): Got service: screensaver
MacBook-Air.local loginwindow[56]: in od_principal_for_user(): No authentication authority returned
MacBook-Air.local loginwindow[56]: in od_principal_for_user(): failed: 7
MacBook-Air.local loginwindow[56]: in pam_sm_authenticate(): Failed to determine Kerberos principal name.
MacBook-Air.local loginwindow[56]: in pam_sm_authenticate(): Done cleanup3
MacBook-Air.local loginwindow[56]: in pam_sm_authenticate(): Kerberos 5 refuses you
MacBook-Air.local loginwindow[56]: in pam_sm_acct_mgmt(): OpenDirectory - Membership cache TTL set to 1800.
MacBook-Air.local loginwindow[56]: in od_record_check_pwpolicy(): retval: 0
MacBook-Air.local loginwindow[56]: in od_record_attribute_create_cfstring(): returned 2 attributes for dsAttrTypeStandard:AuthenticationAuthority
MacBook-Air.local loginwindow[56]: in pam_sm_setcred(): Establishing credentials
MacBook-Air.local loginwindow[56]: in pam_sm_setcred(): Got user: ben
MacBook-Air.local loginwindow[56]: in pam_sm_setcred(): Context initialised
MacBook-Air.local loginwindow[56]: in pam_sm_setcred(): Got euid, egid: 501 20
MacBook-Air.local loginwindow[56]: in pam_sm_setcred(): Done getpwnam()
MacBook-Air.local loginwindow[56]: in pam_sm_setcred(): Done setegid() & seteuid()
MacBook-Air.local loginwindow[56]: in pam_sm_setcred(): pam_sm_setcred: krb5 user ben doesn't have a principal
MacBook-Air.local loginwindow[56]: in pam_sm_setcred(): Done cleanup3
MacBook-Air.local loginwindow[56]: in pam_sm_setcred(): Done seteuid() & setegid()
MacBook-Air.local loginwindow[56]: in pam_sm_setcred(): Done cleanup4