invalid conversion from `const void*' to `void*'

Im trying to implement a THREAD class that encapsulates a posix thread.
Here is an outline of my THREAD class.

class THREAD {

public:
        // returns 1 if thread sucessfully started
    int Start(void* = NULL);

       // other public functions

protected:
    virtual void* Run(void*);

};

int THREAD::Start(void* param) {
    if (!Started) {
        Param = param;
        if (ThreadHandle =
(HANDLE)_beginthreadex(NULL,0,ThreadFunction,this,0,&ThreadID))
        {
            if (Detached)
            {
                CloseHandle(ThreadHandle);
            }
        }
        Started = TRUE;

    }
    return Started;

}

Once the thread is started it basically calls Run() inside the
ThreadFunction.

I have a class called HELLO that inherits from the THREAD class that
simply prints "hello" to the screen.

class HELLO : public THREAD {

protected:
    virtual void* Run(void*);
};

void* HELLO::Run(void* param) {
    char* message = param;
    for (int i=0;i<11;i++)
    {
        printf("%s\n", message);
    }
    return NULL;
}

Problem: when i create a new instance of HELLO and attempt to call
Start("hi") i get the following error under gcc 3.3.5

 error: invalid conversion from `const void*' to `void*'
 error: initializing argument 1 of `int THREAD::Start(void*)'

Under VC++ 8.0 the code works fine. Can anyone suggest a resolution.