I think many issues may cause this error message. Recently I also got this issue all of sudden.
Some people suggest to Repair SharePoint under Control Panel, restarting search servers, reinstall Search Service Application, change the service account, or recreate entirely the search service application and components.
My question is, why it worked before?
Then I noticed the post from Joel Plaut. Joel mentioned that we could change "memoryLimitMegabytes" settings in "noderunner.exe.config" to reduce the memory consumption, that rang the bell in my mind.
I got this problem in Development environment (SP1 + CU201406). Apart from a separate SQL Server instance, the farm contains 2 virtual machines, and each have 8GB RAM. Since I started "Microsoft SharePoint Foundation Web Application" on both servers, the hardware resource is far below the minimum requirement from MSDN.
So, I kept all web applications running on one machine, and moved most of the other services, such as "Search Services" and "Distributed Cache service" to the other VM.
After restarting "Search Host Controller Service", Bing! The problem is fixed!