We just recently stood up Imager Server 10, registered it with AGS, and have created and compiled our first image service. The Server reports that things are good...the Service Provide reports that things are good...but every time I try to publish our service I get the error "ISCDef does not exist", although I am able to clearly point Server to the file to in order to try to publish it. The SOC has access to the directory where these files are stored, and has been able to serve map services with no problems.
Well I tried going in and changing all of the Image Server services to run as our domain SOC account, as this is the account we created for Server administration so that it could see the data on our share drive, but the Image services will not start up using this account...they will only start using the Local account. Server logs aren't showing any errors at all...Image Server log just says the same thing the error says...
Note that the Service Provides by default runs as user SYSTEM. In this case I believe that SYSTEM does not have access to the directory in which the ISDefs are stored. I'm presuming this directory is on some Network. Best to either specifically give SYSTEM access to the network or change the login for the Service Provider to another user that does have access.
Naturally the preferred solution at V10 would be to create Mosaic Datasets (instead of ISDefs) and serve these as image services. When Serving Mosaic Datasets these are accessed using the ArcGIS standard SOC/SOM and there is no intermediate Service Provider.