Broken Google Play on cm 10.1.2
The error [RPC:S-5:AEC-0] is down to having to remove your google account and re-add it again. 

If your account is primary google account, the only way you can remove it is to factory reset and re-install everything! That is the only known cure and quoted by Google themselves! Do not think they are taking it seriously enough. It broke on a previous update to Google Play Store about two months ago.

I get that too, if keep trying over a few minutes, it will eventually update, not successfully though. 

I do think its more of an issue on the Google system itself in conjunction with Play store app. 

It's not just confined to AOSP JB/ICS or CyanogenMod, I get in on Gingerbread too.

PS: As matter of curiousity - do you have Google 2-step account verification active on your account?