[Plugin: WordPress SEO by Yoast] Yoast SEO giving blank page upon activation

I’m running Graph Paper Press modularity theme. When I activate the WordPress SEO plugin, I get a blank screen everywhere apart from my home page. I haven’t enabled any SEO options yet and all other plugins are off, just to test.

Have ensured clean permalinks is off in SEO > permalinks as per FAQ. Can’t figure out what must be a no-brainer….

Any sugestions very welcome. Have disabled the plugin right now, but can re-enable if needed at http://www.neillwatson.com

Thanks in advance

Neill W

http://wordpress.org/extend/plugins/wordpress-seo/