Use Entity Manager on server. How?

An EntityManager can only execute on a single thread. This EntityManager is authorized to execute on the thread with id=’13’; the requested operation came from the thread with Id=‘14’.

I have silverlight application that uses Model on a client. 
I also have mobile clients that connect to the same server (WCF REST)

I'm using EntityManager on server as well but get errors like:

An EntityManager can only execute on a single thread. This EntityManager is authorized to execute on the thread with id=’13’; the requested operation came from the thread with Id=‘14’.
Consider calling the EntityManager’s asynchronous methods; they work safely on background threads managed by DevForce. 
You may have to disable this cross-thread checking for specific reasons such as automated testing. Please review our documentation on multi-threading issues and the EntityManager.AuthorizedThreadId property.

What does it mean and how do I work with it? Prior to getting DevForce we used EF and there was no issues like this. We don't want to maintain 2 models with the same stuff and converted to DevForce. 

Mobile service looks like this:

[Export]
    [PartCreationPolicy(CreationPolicy.NonShared)]
    [ServiceContract]
    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
    [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
    public class MobileService
    {
        [Import] 
        public IContextManager ContextManager { get; set; }
        [Import]
        public IMembershipService MembershipService { get; set; }

So, that means I'm having instance per call. However my ContextManager and MembershipService shared and I guess this is where the problem is. I understand I can make them non-shared. Or is there other way to solve this problem?

I realize that I probably should do single instance per-call which means I should use NonShared on all of my DI-objects.

I wonder how DevForce will perform in such scenario? I have very light DB calls (small inserts) but there is a lot of calls. Up to 1000 per minute which means I will have to create EntityManager instance every time. Is that a big load? Or it will be fine?

Edited by katit - 01-Feb-2012 at 2:51pm