That is a known issue fixed a long long time ago:
To prevent future occurrences of this PSOD:
Update to a minimum of ESXi 5.1 Update 2.
or as a workaround:
Use VMXNET3 virtual adapters instead of e1000 on all VMs.
Or if this is not possible, in VMs that use the E1000e adapter, disable RSS or configure the RSS multiple rx queue to 1 in the guest OS.
Thank you for you response. You right, I have an old version of ESXi 5.1..
It's scary to update because a full backup of VMs is hard to do. And it is terrible to lose in case something goes wrong when upgrading.
In any case, you really helped me. Thanks!