[WP Super Cache] Error: undefined function prune_super_cache

Hello,

I moved my blogs to a new server and I wanted to clear everything.

I’m facing an issue when I try to “manually” delete cached files :
In WP Super Cache plugin, on Content tabs, I click on “List all cached files”. Then I click on “x” to delete the first on the list, and I get this error :

Cache Contents
Deleting supercache file: xxxxxx
Fatal error: Call to undefined function prune_super_cache() in .../plugins/wp-super-cache/wp-cache.php on line 2045

It seems the cached page is deleted after all, but I have that error each time I click to delete a page …

Is there something missing on my new server ?

Is it safe to delete the whole content of “wp-content/cache/supercache/www.myblog.com/” ?