Good news (for me)
After replacing my OnBoard NIC with one for the PCI Slot (an Intel Card with Intel 82541PI Chip), the problem doesn't occur anymore.
So it seems likely that the issue has something to do with the Realtek Chip, as Grondr stated.
Good news (for me)
After replacing my OnBoard NIC with one for the PCI Slot (an Intel Card with Intel 82541PI Chip), the problem doesn't occur anymore.
So it seems likely that the issue has something to do with the Realtek Chip, as Grondr stated.