Like @rackandboneman says, ESXi 5.0U1 with the free licence broke autostart of VMs. I updated, but had to roll back, because I rely on autostart. Here's a thread on HardForum where a VMware employee (lopoetve) confirms it: http://hardforum.com/showthread.php?t=1681128
If you are running the free version of ESXi (aka ESXi Hypervisor) then you'll want to be aware of a critical issue that surfaces after upgrading to 5.0 Update 1. I want to stress this only applies to people runing the free ESXi version. If you're ESXi hosts are licensed this issue does not affect you.
There were some changes made in the way the ESXi APIs are accessed in Update 1 that unfortunately breaks the VM Auto Start feature in the free ESXi version. Please note that this issue only affects the free ESXi version and it was not intentional.
If this is Esxi 5.0U1 with the free license, autostarting VMs is known broken.
Like @rackandboneman says, ESXi 5.0U1 with the free licence broke autostart of VMs. I updated, but had to roll back, because I rely on autostart. Here's a thread on HardForum where a VMware employee (lopoetve) confirms it: http://hardforum.com/showthread.php?t=1681128
Here's an official blog post confirming the issue, and explaining it in more detail, aswell as rollback guide: http://blogs.vmware.com/vsphere/2012/03/free-esxi-hypervisor-auto-start-breaks-with-50-update-1.html
More detailed rollback guide: http://boubchir.co.uk/vm-blog/roll-back-esxi-5-0-update-1-to-esxi-5-0/ (Do at your own risk!)
I wrote a blog post a couple of days ago that has a workaround for this. Hopefully someone will find it useful :)
www.liberux.com/virtualization/vmware-esxi-5-0-u1-doesnt-auto-start-virtual-machines/