I have a wordpress site which GWT reports hundreds of 404 errors, when trying to inspect the 'alleged' pages that output those dead links I find nothing.. There's something very particular in those errors, they are all long numbers (integers) appended to the url after a category, so it usually looks like .com/category-name/1234556780000

The theme is a custom theme I built and the site currently runs wp3.4.2 and the following plugins:
- Custom Post Permalinks
- Disqus
- Gravity Forms + Mailchimp add on
- Wordpress SEO (yoast)
- Geolocation
- YARPP

Any help or steps to try would be appreciated!
Thanks!
ps. EDIT: I know its somewhat similar to Wordpress translator plugin: Google Webmaster's Tools shows hundreds of 404 not found errors. How to clean the mess? but I never used that plugin..