I agree that it could very well be malware (browser hijacker).
Try uninstalling your current antivirus if you have one
and then download and run both MSE (Microsoft Security Essentials)
and MalwareBytes to see if anything can be found and quarantined.
Get MSE here:
Microsoft Security Essentials - Free Antivirus for Windows
Get MalwareBytes here (look for the free version):
Malwarebytes : Free anti-malware, anti-virus and spyware removal download
Good luck
Edit: I know you say that you are using IE8 but have you thought about updating to IE9. Your browser (being the second largest piece of software after your OS) should be kept updated as the latest version will have bug fixes.
Also, try using Firefox to see if the redirections are consistent in both IE and Firefox. If you have the same problem in Firefox then it could be something else.
Back again: I also have one more suggestion for you - restore internet explorer settings and advanced settings:
Internet options -> Advanced tab