Hi Markus, Wine development is driven by test cases checked in to the Wine source tree. Please extend the test cases in dlls/oleaut32/tests to verify that oleaut32 is caching BSTRs properly, and make sure that test passes on Windows and is marked todo_wine. Once we have a test case like that checked into the Wine source tree, we'll be in better shape to accept a patch that fixes bug 12460. Thanks!