Is there a delay in what's available via auto-update and updates that are available for manual download through cisco.com? I noticed today that S498 became available yesterday, but my IPS module in my ASA hasn't downloaded it automatically yet. When I do a #sh statistics host, I have a recent download attempt that says "Success: No installable auto update package found on server.
Just wondering if there is a delay between manual and auto updates or if I need to be concerned that my auto-udpates aren't working properly.
It sounds like you are encountering bug CSCsq53214.
The fix is, as you asked, to reboot the module. You should be able to confirm current signature update from the output of 'sh ver' issued on the CLI.