ian_perkins
El Capitán's new System Integrity Protection breaks the SME client for Mac. The fix is to disable SIP, as outlined here:

http://www.imore.com/el-capitan-system-integrity-protection-helps-keep-malware-away

Perhaps the next version of the client will work with SIP, so that it can be enabled.
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ian_perkins
As an addendum, it seems that SIP is re-enabled after each shutdown/restart, which is a PITA...
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