The download page for Windows Adobe Reader updates does not list the 9.3.1 update.
As of 5:20pm EST 2/17/10, this page does not list the 9.3.1 update. I see the link for the full download of version 9.3 and links previous update (9.13, 9.1.2,, etc). Looking at the download URL for 9.1.3 (old update), I guessed at the URL for 9.3.1 (most recent update). It works and I get a file named AdbeRdrUpd931_all_incr.msp. I have the Linux update and I see where the Mac link now works. Hopefully, someone will fix the page so I can patch my department's ~180 PCs before my users hurt themselves running with scissors opening malicious PDFs.
Okay, it's fixed now. However, to a prior poster's point, there seems to be no rhyme or reason to the sort order in the table for updates. Old updates listed before new updates which are then followed by intermediate updates.
Good sense overwhelms me and I decline to further question the judgement of the thousand monkeys at a thousand HTML editors who manage the Adobe.com website. I'm downloading my monthly CRITICAL-OH-MY-GOD-PATCH-IT-NOW update and going home. I miss blink tags.