Take a look at this thread discussing the same question.
http://h30499.www3.hp.com/t5/Quality-Center-Support-and-News/QC-license-usage-amp-failed-login-attempts/m-p/5827115#M74333
http://h30499.www3.hp.com/t5/Quality-Center-Support-and-News/QC-license-usage-amp-failed-login-attempts/m-p/5827115#M74333