[STAThread] and [MTAThread]

STAThread stands for SingleThreadApplicationThread, meaning
that your application is limited to its own single thread.
This is required for certain things like Dynamic menu items
to work in Win98/ME.


Including the [STAThread] attribute indicates that the
default threading model for an application is single-threaded
apartment (STA).


Any public static (Shared in Visual Basic) members of this type
are safe for multithreaded operations. Any instance members are
not guaranteed to be thread safe.

Threading models only pertain to applications that use COM
interop. Applying this attribute to an application that does
not use COM interop has no effect.

The startup threading model can be set to single-threaded apartment
or multithreaded apartment. If it is not set, then the thread
is not initialized.

WMI provider COM objects are "free" threaded, that means they
need to run in a MTA thread.  When your main thread is initialized
for STA, the Management classes check the current apartment for
MTA compatibility, and will create a new thread and enter the MTA
to create the COM objects, COM will marshal the interfaces
between the STA thread (running your managed code) and the MTA
thread running the native COM code.

But, your main thread (STA) has enabled the SeSecurityPrivilege for the main
thread, but this privilege is not propagated to the MTA thread, resulting in
an access denied exception.
Therefore I suggest you allways run your code on an MTA thread, the net
benifits are
- no marshaling overhead
- no difficult to track security issues.
- no issues due to eventsink marshalin between MTA and STA threads.

There is a known bug in System.Management.dll in .NET Framework v1.0. The bug
that prevents WMI privileges from propagating from managed code running on
STAThread to WMI core. Applying [MTAThread] to the calling thread appears to
be a partial workaround to this problem as Access Denied would still be
returned on the second time of event subscription. This problem should be
fixed in .NET Framework v1.1. Have you tried running your application with
v1.1?