A possible cause is a video published on the RNW Arabic site which shows a migrant being beaten up in Saudi Arabia.
The Saudi authorities’ message says: Sorry, the requested page is unavailable. If you believe the requested page should not be blocked please click here. The link in the message points to the website of the Communication and Information Technology Commission (CITC), where unblocking requests can be made. It is unlikely that many web users click on the link. It could lead to an unwanted ‘courtesy call’ from the authorities.
More:
http://www.rnw.nl/english/article/saudi-arabia-blocking-rnw-websites