A few Virtualcenter users are reporting the following error when trying to start Virtualcenter:
Failed to initialize: not well-formed (invalid token)

The problem seems to happen if one or more ESX hosts being managed have Update 2 on them, but Virtualcenter itself is running Update 1 or earlier.
The problem doesn’t show right away.  Not until Virtualcenter [...]

Many customers are hitting a new bug in ESX preventing them from powering on virtual machines or VMotion them.  There is a published knowledge base article on this which reads>>
Unable to Power On virtual machine with “A General System error occurred: Internal error”
A virtual machine fails to power on, fails to leave suspend mode, or [...]

With the new Virtualcenter 2.5 Update 2 comes some tighter restrictions on HA network configurations.  This error message commonly occurs when the nodes in a cluster contain incompatible networks. An attempt to reconfigure clusters might fail now if they do not have identical networks.
Some customer are reporting the message:

HA agent on <esxhostname> in [...]