I have encountered this issue several times and each time, thus far, it was related to a virus or malware that was infecting the PC. In each case these systems had Antivirus or Internet Security installed. NO Antivirus or Internet Security program is 100%. If you have these issues you may want to perform a FREE online scan of your PC from one of the following companies. PLEASE READ THE INSTRUCTIONS BEFORE PERFORMING SCAN.
Trend
http://housecall.trendmicro.com/
BitDefender
http://www.bitdefender.com/scanner/online/free.html
ESET
http://www.eset.com/us/online-scanner/
Microsoft
http://www.microsoft.com/security/scanner/en-us/default.aspx
McAfee
http://home.mcafee.com/Downloads/free-virus-scan
Norton
https://security.symantec.com/nss/getnss.aspx?langid=ie&venid=sym
