Hi @sremy,
Sorry to hear of the problem you are having.
Could you please try using the solutions posted in the following replies to resolve this issue?
http://premium.wpmudev.org/forums/topic/10002-authenticationauthorization-failed-you-do-not-have-permissions-to-make-this-api-call#post-579631
http://premium.wpmudev.org/forums/topic/10002-security-error-security-header-is-not-valid-5#post-792833
Best Regards,
Vinod Dalvi