When starting an OS X guest under VMware Fusion with more than 1 vCPU, the following warning message is displayed:

[2013-12-30013036]  VMware Fusion-VMware Fusion

To disable the message open the VMX file for the guest whilst it is shutdown and add the following line:

This only suppresses the message, and the guest may be more unstable with more than 1 vCPU.

Suppress VMware multiple vCPU message