Memory corropt error

Recently, I have installed QC 11 and In some of my projects I have problem with generating reports and drag & drop of test cases; I get this error: "Attempted to read or write protected memory. This is often an indication thet other memory is corrupt." .

But when I drag & drop a folder of test cases, it is ok and I think this is the sign of not having memory corruption. Does any one know about the reason & the solution for this problem?