Experiencing an issue with the WAN fall back feature in the SA520? The latest firmware release resolves the problem. You can download the software here:
http://www.cisco.com/cisco/software/navigator.html?mdfid=282414017
You can find more information about the software in the Release Notes here: http://www.cisco.com/en/US/docs/security/multi_function_security/multi_function_security_appliance/sa_500/release/sa500_MR3_v2.1.18.pdf.