I'm receiving excessive error messages in my console: http://pastebin.com/Hx2jyFS3

Thank you for the report, I will take a look.

I couldn't overlook plugin Timeismoney v1.5 throwing exceptions as well. Please try uninstaling said plugin and check if issue persists.
Also, is player "Zakhep" real player or an NPC ? If its an NPC, please let me know what NPC plugin you are using.

Are you still getting the error? What quester build/version were you using when it appeared? It appears this error is not present in quester anymore.