have you manually deleted all files & folders under "/core/cache/" folder ? do that from your hosting file manager.
[ed. note: gee last edited this post 13 years, 1 month ago.]
Or..you might wash out your config.core.php and /core/config/config.inc.php while upgrading, preserve these two files, I've experienced this kind of issue times ago..
Yes..the config files are the files you wont upgrade..it tells you about the paths of your resident system, dont' forget the configs under /manager and /connectors as well..preserve them also.