Thanks all, and sorry for the slow reply - didn't realize that J-Net didn't automatically subscribe you to threads you initiate.
lpaniagua - I've set my logging per your suggestion and found no other relevant messages than those that Pradeep posted earlier:
May 21 06:44:25 SRX100JS checklogin[3446]: warning: can't get client address: Bad file descriptor May 21 06:44:25 SRX100JS checklogin[3446]: WEB_AUTH_FAIL: Unable to authenticate httpd client (username juniper)
I would love to open a JTAC case, but don't believe that I can since the SRX100 is EOL. Additionally, because of that fact, will future SRX firmware updates even support the SRX100?
I will be back onsite with this device Thursday and will be able to test downgrading the firmware then. Do we know if this issue was present on version 12.1X46-D82? We skipped a few versions, so cannot confirm.