I have configured HTTP upload "by the book", using the pre-packaged web application in
"installer directory"\Content Delivery\roles\upload\dotNET\webapp\x86_64\upload.zip
When accessing the HTTPUpload.aspx page to test it, I get the following error:
A process serving application pool 'upload.visitorsweb.local' suffered a fatal communication error with the Windows Process Activation Service. The process id was '3812'. The data field contains the error number.
I can see that sometimes when this happens, the application pool stops, but re-starting it doesn't help. The only useful item in the logs seems to be the message above.
I'm running Windows Server 2012 using SDL Tridion 2013.
What might be the cause of this, and where could I investigate further?
EDIT: Note that the error above was found in the Windows logging. The log files you might have expected to be generated by Tridion CD libraries were entirely empty. In the light of the eventually discovered cause, this is a significant diagnostic indicator.