NAC 3.5 on 2008 R2 (64-bit) IIS Applications Cannot Start

we have an issue whereby the NAC server is running on a 2008 VM, half of the applications in the IIS 7 application pool are running, so I can login and browse some of the interface. However the following services are not started and when I attempt to start them manually I get an error

Policy App Pool

Registration App Pool

Report App Pool

Server Status Pool

I get the the following error in the servers system log that tie in with attempts to start the applications, I have reset and tested the logon that the services use

"DCOM got error "1326" and was unable to logon NAC1\SophosNAC in order to run the server:

{A2287806-D5E1-414C-8C0C-9C8854B9171D}"

Any help would be appreciated!