I came across an issue where a blade (host) had been changed overnight but authentication was failing due to the time on the host being out of sync with the other hosts in the cluster.

The ntp deamon was running, NTP was contactable, but was too far out so could not correct the time.
If the hwclock on replacement hardware is more than 1000S out then ntpd cannot correct the time.
Read here: http://doc.ntp.org/4.1.0/ntpd.htm

Here is a very quick PowerCli check you can do in your environment to make sure NTP is working and correct before you lose a lot of time troubleshooting:

Get-VMHost | Sort Name | Select Name,
@{N=”NTPServer”;E={$_ |Get-VMHostNtpServer}},
Timezone,
@{N=”DifferenceTime”;E={(Get-View $_.ExtensionData.ConfigManager.DateTimeSystem) | Foreach { ($_.QueryDateTime().ToLocalTime() – [DateTime]::UtcNow).TotalSeconds}}},
@{N=”ServiceRunning”;E={(Get-VmHostService -VMHost $_ |Where-Object {$_.key-eq “ntpd”}).Running}} `
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