IIS cannot access DFS after reboot.

I have an issue where one of my IIS servers cannot access DFS until a user logs into the server. No action is required by the user other than logging into the server using RDC.

Until a user logs into the server the site returns a 500 error code. Other sites hosted on the same server which do not use DFS run normally.

Although Failed Request Tracing is turned on nothing gets logged while the site is down. Once IIS can access DFS Failed Request Tracing works normally. IIS logs just show 500.19 errors with sc-win32-status of 4350.

Any ideas on how to troubleshoot this issue would be appreciated.

Thanks,

Hugh