Hi Jeff,
thanks for your answer, anyway this not fix the issue.
I disabled HPET at the OS level following the documentation, and disabled HPET on the Virtual Machine also (hpet0.present=FALSE on the ESXi VM configuration), but nothing changed. In my previous post I forgot to specify that I installed HMP on a Virtual Machine on ESXi 5.5, do you think the issue could be related to VMware environment?
Roberto