See here: http://kb.vmware.com/selfservice/viewContent.do?externalId=1010215&sliceId=1
-KjB
VMware vExpert
Hi KjB,
we have an other error message and it stops at 24%, not 26.
I have try the solution and power off the ESX after error, but ESX 3.5 boots normal up.
Regards
Christian
it seems its a knows issue in Upgrade. see the Upgrade issues in ESX 4.0 relase notes "http://www.vmware.com/support/vsphere4/doc/vsp_esx40_vc40_rel_notes.html#upgradeissues".
You can try out the following workarond mentioned in the RN.
*Workaround: Close and restart the vSphere Host Update Utility. Then run the host upgrade. *