wordpress, php: print_r(): Cannot use output buffering in output buffering display handlers

I’m getting this message when trying to access wp-admin.php of my website:

“Fatal error: print_r(): Cannot use output buffering in output buffering display handlers in /home/x/public_html/wp-content/plugins/wp-super-cache/wp-cache-phase2.php on line 253”

Around the line 253, there’s some statements:

// All the things that can stop a page being cached
$cache_this_page = true;
if ( defined( 'DONOTCACHEPAGE' ) ) {
    wp_cache_debug( 'DONOTCACHEPAGE defined. Caching disabled.', 2 );
    $cache_this_page = false;
} elseif ( $wp_cache_no_cache_for_get && false == empty( $_GET ) && false == defined( 'DOING_CRON' ) ) {
    wp_cache_debug( "Non empty GET request. Caching disabled on settings page. " . print_r( $_GET, 1 ), 1 );
    $cache_this_page = false;
}

And some other elseif statements after that.

A quick look in WP-forums shows that I’m not alone on this. Some people fixed it deactivating the plugin wp-super-cache, but I prefer an alternative solution, until the devs of this thing fix it.

Any ideas?