Had an issue today where tasks sequences which had been running fine for months suddenly stopped running fine.
After some investigation, I found the content was being delivered, even though the cas.log indicated content locations had been found.
Turned out the datatransferservice.log had the following error logged
Error sending DAV Request.HTTP Code 500,Status ‘Internal server Error’.
Browsing to the http://localhost:80/SMS_DP_SMSPKG$ also threw a HTTP 500 error.
An IIS reset didn’t help, so I did a quick search and found http://eskonr.com/2014/01/sccm-configmgr-2012-error-sending-dav-request-http-code-500-status-internal-server-error-datatransferservice-log/
Setting the application pool back to “Enable 32-bit applications = False” worked immediately.
As to why it had been changed… an IT person was testing a new web app and decided to use the SMS Distribution Points Pool for some reason….