even I had similar issues, i have uninstalled qt 4.8.4 and reinstalled QTv4.8.5, and it solved the problem on one mission which runs on VS2008, but i’m still having similar issue on a machine in which im having VS 2010, and im finding the correct version of QT required.
but for your case, i believe reinstalling QTv4.8.5 may resolve the issue.