Cast received object to a List<object> or IEnumerable<object>

Question

I'm trying to perform the following cast

private void MyMethod(object myObject)  
{  
    if(myObject is IEnumerable)  
    {
        List<object> collection = (List<object>)myObject;  
        ... do something   
    }  
    else  
    {  
        ... do something  
    }  
}

But I always end up with the following excepction:

Unable to cast object of type 'System.Collections.Generic.List 1[MySpecificType]' to type 'System.Collections.Generic.List 1[System.Object]'

I really need this to work because this method needs to be very generic to receive single objects and collections both of unspecified types.

Is this possible, or is there another way of accomplishing this.

Thank you.

How to solved?

C# 4 will have covariant and contravariant template parameters, but until then you have to do something nongeneric like

IList collection = (IList)myObject;