Three things to try:
1. Manually delete all files in the core/cache directory.
2. Make sure you have this tag (with the exclamation point) in the head section of all templates:
<base href="[[!++site_url]]" />
3. Visit the site with your browser in private or incognito mode.
I remember some users have said to be extra sure you can go into your server with ftp and delete everything in cache. Sometimes apparently the graphical file manager will hide some files and then they won't get deleted unless you do it on the server.
My own experience is its not needed, just thought it could help
