I'm using PHP5 and WordPress 3.1.
I just upgraded to Sexybookmarks 3.3.5, tried to "resave the settings" as prompted, but get this error in the settings screen:
Fatal error: Cannot use object of type WP_Error as array in /home/mysite/public_html/wp-content/plugins/sexybookmarks/sexy-bookmarks.php on line 497
I then deactivated Sexybookmarks 3.3.5, and reactivated it again, but still get the same error.
So I've uninstalled 3.3.5 and gone back to 3.3.4 without any errors.