Hello [FIRSTNAME], thank you for your patience!

It appears that something has come up that is causing MCPC+ to malfunction. 
Here's a little bit of information from MoJang Support twitter:
Regarding the issue at hand https://twitter.com/MojangSupport/status/448924619773186048 
Regarding a possible fix: https://twitter.com/MojangSupport/status/448930853083553792

This appears to only effect our users using Spigot, in our case, MCPC+.

We are aware of this issue, and presently do not have an ETA on an actual fix. 

We are currently recommending that you try installing the latest version of MCPC+ for the Minecraft version that you are using  to your server in an attempt to rectify the situation. For Minecraft 1.6.4 this build will be found at http://ci.md-5.net/job/MCPC-Plus-164/251/ 

We thank you for your patience!