We recently posted the VMM 2012 error codes to the TechNet wiki. The main page is located here: http://social.technet.microsoft.com/wiki/contents/articles/4906.aspx.
For each error code, the error or warning message and recommended action is listed. The recommended action is the in-product troubleshooting information that is displayed together with the error or warning message. There’s also an Additional Troubleshooting Information column. This is where you can all help add value. If you know more about how to troubleshoot an error than what is included in the Recommended Action (in product) column, please edit the wiki page to add that information. To edit you need to sign in with a Windows Live account. For information about how to join the wiki, see http://social.technet.microsoft.com/wiki/contents/articles/129.aspx.
(Note that the VMM 2008 R2 (including SP1) error codes are also posted to the TechNet wiki at http://social.technet.microsoft.com/wiki/contents/articles/virtual-machine-manager-vmm-2008-r2-error-codes.aspx.)
VMM Content Team