Look at the InnerException property of the exception that is thrown to get a more specific error message.

There are at least two types of .NET attribute. The first type I will refer to as a metadata attribute - it allows some data to be attached to a class or method. This data becomes part of the metadata for the class, and (like other class metadata) can be accessed via reflection. An example of a metadata attribute is [serializable], which can be attached to a class and means that instances of the class can be serialized.

[serializable] public class CTest {}

The other type of attribute is a context attribute. Context attributes use a similar syntax to metadata attributes but they are fundamentally different. Context attributes provide an interception mechanism whereby instance activation and method calls can be pre- and/or post-processed. If you have encountered Keith Brown's universal delegator you'll be familiar with this idea.

CAS is the part of the .NET security model that determines whether or not code is allowed to run, and what resources it can use when it is running. For example, it is CAS that will prevent a .NET web applet from formatting your hard disk.

The CAS security policy revolves around two key concepts - code groups and permissions. Each .NET assembly is a member of a particular code group, and each code group is granted the permissions specified in a named permission set. For example, using the default security policy, a control downloaded from a web site belongs to the 'Zone - Internet' code group, which adheres to the permissions defined by the 'Internet' named permission set. (Naturally the 'Internet' named permission set represents a very restrictive range of permissions.).

Caspol has a couple of options that might help. First, you can ask caspol to tell you what code group an assembly belongs to, using caspol -rsg. Similarly, you can ask what permissions are being applied to a particular assembly using caspol -rsp.