Why doesn't the VS2005 debugger show the actual 'this' address?

I'm using VS2005 debugger and noticed something I wasn't expecting and was hoping there was a simple answer: (I know: upgrade ... unfortunately stuck with it and can't...)

I have a function where I'm dumping the address for debug tracking:

int myclass::myfunction()
{
    myclass *pThis = this;
    TRACE("inside myfunction - this=0x%08x, pthis=0x%08x\n",this,pThis);
    ...
}

The trace output shows that pThis=this (in this case both=0x0e23ff90), but if I hover the mouse over the two, pThis=0x0e23ff90 and this=0x0e23fff0! (The debugger expands both to show the same data.)

Can someone tell me why the debugger shows 'this' as 0x0060 higher than it really is?

Thanks!

DanWoerner