It looks like there is a conflict with the ST-Link/V2-1 driver.
You can try this solution : http://www.openstm32.org/tiki-view_faq.php?faqId=1#q3
Or reinstall the driver providen by ST.
Here the link to download the latest ST-Link/V2-1 driver (Vista, Win7, Win8) : http://www.st.com/web/catalog/tools/FM147/SC1887/PF260218
Hope it will solve the problem,