You don't give us much to work with. Have you tried re-typing the URL for your homepage> Tools> Internet Options> General tab> Homepage section> Use Current?

Have you also deleted the temporary internet files and Cookies? Where are you being redirected to?

Does that restore the homepage? Does it stay on the browser?

I have notices that occasionally a homepage, especially one that has been customized might have a small code change that will prevent it from launching without incident. Deleting the 'tif' and resetting it usually works if this is the cause.

Description of hrena.com, which is a search hijacker that is installed by a Trojan.

http://www.precisesecurity.com/blogs/2007/07/11/hrenacom/

Please follow kimsland lead to begin the malware cleaning process.