Calling a com object from defferent thread

I'm creating a ATL class. In a member method I'm invoking a seperate
thead. I'm Also passing the current Atl call instance as a argument to
this thread. Actually this thread is created by a library. So I have no
control over it. Thread accepts a void pointer. So when I retreive the
Atl class I have to cast it.

CAtlClass::method()
{
 //this method will create a new thread. I'm passing a Pointer to my
current object using "this" pointer
    invokeingMethod(this);
}

CAtlClass::method2(int value)
{
 m_value = value;
}
The thread calls a another funtion. Which is a C style global function.
I can access AtlClass object from this method. This is a general sample
of that method.

threadMethod(){
//I'm accessing my atl class via the void pointer
   CAtlClass *instance = (CAtlClass *)(stored void pointer);

//I'm calling my AtlClass method via this retrieved pointer
    instance->method2(10);
}

When I'm calling methods like this the actual method is calle. But
inside the methods nothing happens. For example in the statement
m_value = value; the value I passed via the thread method is not
assigned to the member variable. What is the wrong with this method.
I'm new to ATL. So I have no Idead what is happening. Thanks inadvance