[Role Scoper] flush_rewrite_rules in plugin init causes DNS timeout

If flush_rewrite_rules() is included in an init action, my plugin’s permalink rules are followed, but I experience various DNS timeouts in the dashboard like when searching for new plugins and get the following:

An unexpected error occurred. Something may be wrong with www.remarpro.com or this server’s configuration. If you continue to have problems, please try the support forums.

But if I flush as part of plugin activation as per the codex, the permalink changes do not take effect, although I do not get timeouts.

A plugin with just the following is enough to cause the problem:

add_action('init', 'sfs_foo');
function sfs_foo() {
  flush_rewrite_rules();
}

Suggestions on how to fix this?

UPDATE: It seems to only occur when Role Scoper is activated.