WPMU Hook for archive or deactivate blog?

According to wpseek.com, there exist hooks for unarchive_blog, archive_blog, and deactivate_blog. You can examine them in the source on WordPress’s Trac site:

• archive_blog
• unarchive_blog
• deactivate_blog

All of them use the $blog_id parameter. Try changing your function to reflect that:

add_action( 'archive_blog', 'wp_clear_cache_custom' );
function wp_clear_cache_custom( $blog_id ) {
    wp_cache_clear_cache( $blog_id );
}