Error using "Autofit"

When I use Autofit like in this case:

{
        Excel_2k::RangePtr R1;
        R1->AutoFit();
        return true;
}

And then I compile in "RELEASE" mode, this error appears at the end of
the 
compilation:

"Must take address of a memory location".

No error if it is compiled in "DEBUG" mode.

Any idea??