Simplepie error

With version 1.1.8 activated, the RSS feeds for the WP Development blog and new plugins in the dashboard do not display. The server error log shows numerous messages of this form:

PHP Fatal error:  Cannot make static method SimplePie_Cache::create() non static in class WP_Feed_Cache in /home/les/sites/losingit.me.uk/public_html/wordpress/wp-includes/class-feed.php on line 16, referer: http://losingit.me.uk/wordpress/wp-admin/

Deactivating Garmin Connect restores normal service. I think this is a version incompatibility – WordPress 3.5 comes with Simplepie 1.3.1, the plugin has 1.3.

http://wordpress.org/extend/plugins/garmin-connect/