Unable to power on virtual machines. VI Client displays the error:
A General System error occurred: Internal error.

VMware released Express Patch for this
http://vmware.com/landing_pages/esxexpresspatches.html

The Quick & Easy way to Install the patch is as follows

Shutdown all the VM’s. The Update will reboot the ESXi host

1. Connect the VI Client to the host that needs to be updated.
2. Choose Start > Programs > VMware > VMware Infrastructure Update. (this is installed during the VI client install for ESXi)
3. On the Hosts tab, select the ESXi hosts to check for updates.
4. On the Updates tab, click Check Now.
5. Install the Update. This will download the Update.
6. Once the update is downloaded, will prompt for authentication for your ESXi host and install the update.
7. From VI Client, reboot the ESXi host

If VMware Infrastructure Update is not installed, reinstall  VMware Infrastructure Client and Select during the install. Its part of that