vMotion Error : Failed to write.

While trying to Migrate some machines (Cold and Hot Migrations) from my old 3.5 farm to my new shiny vSphere lab, I received the following error : A general system error occurred: Failed to write to <Path>.
Turns out that Update Manager had filled the vCenter Hard Drive with patches using up all available space on my Single Drive VM. (Normally I point UM patches to a D drive but this was my Lab!?!) 🙂
Cleared up some space on the drive and my Cold and Hot migrations went though without a hitch!