500 Internal Server Error when attempting to query ProGet nuget feed

(x/posted from Octopus Deploy support: http://help.octopusdeploy.com/discussions/problems/26973-500-internal-server-error-when-attempting-to-query-proget-nuget-feed)

We are attempting to set up an internal ProGet server in order to have multiple different nuget package repositories available for use. When attempting to query one of the nuget feeds from ProGet, I receive a 500 Internal Server Error. When looking at the logs in ProGet, it appears as though Octopus is attempting to authenticate as its AD computer account, instead of the account specified in the External Feed configuration.

From ProGet: 
Event code: 4010 
Event message: An unhandled security exception has occurred. 
Event time: 11/18/2014 11:00:08 AM 
Event time (UTC): 11/18/2014 4:00:08 PM 
Event ID: 6e510c1922d9469990beedadc30acc3e 
Event sequence: 4 
Event occurrence: 3 
Event detail code: 0 

Application information: 
    Application domain: /LM/W3SVC/2/ROOT-1-130607997643014658 
    Trust level: Full 
    Application Virtual Path: / 
    Application Path: C:\Program Files\ProGet\WebApp\ 
    Machine name: VMSKY-NUGET 

Process information: 
    Process ID: 1880 
    Process name: w3wp.exe 
    Account name: NT AUTHORITY\NETWORK SERVICE 

Request information: 
    Request URL: https://nuget.company.com:443/nuget/Developer 
    Request path: /nuget/Developer 
    User host address: 10.1.0.23 
***** User: VMSKY-DEPLOY$ ***** 
    Is authenticated: True 
    Authentication Type: 
    Thread account name: NT AUTHORITY\NETWORK SERVICE 

Custom event details:

In the ProGet IIS site, Forums Authentication and Windows Authentication are enabled in order to allow our developers access to the web interface. I do not know if this would be an item I need to solve in Octopus or ProGet, or where a configuration change might be needed for this.

Product: ProGet
Version: 3.2.1

This is a client-side issue; ProGet cannot control what credentials are sent to it (it can only request they be sent :) ). Could you configure the Octopus service to run as a domain user, then assign privileges to that user instead of specifying them in its external feed configuration? I am not familiar enough with Octopus to know if that's a possibility or not.

Thanks for the suggestion, Tod. That does solve the issue I'm seeing and ProGet appears to be functioning completely normally, so I'll just have to follow up on the Octopus Deploy side. This isn't what I would call an expected behavior; it's certainly possible I have something misconfigured as well.

Have you looked at ProGet's deploy features? We switched to using those from Octopus, sooo much simpler for our configuration (no agents... plus we could just do a choco install if we needed to), and you could add w/e pshell scripts you wanted.