Not sure if this question is relevant to your team. I have been having difficulty accessing to my website's administration panel 'it says invalid security token' both in Chrome or Explorer, even though I have cleared my browsing history.
1. log in to front end of your site - using your admin details
2. log out of frontend
3 clear browser cache (and site cookies)
4. log in to backend of site should then work.
Regards, Mark.
Please search forums before posting. Please make sure your post includes the version of the CMS you are using and a link to the problem. Annotations on screenshots can also be helpful to explain problems/goals. Please use the "secure" tab for confidential information.