em0 freezes on ZFS server

[Willem Jan Withagen]

Hi,

I build an ZFS server based on
	Supermicro C2SBX with 8Gb and intel Q9550
http://www.supermicro.com/products/motherboard/Core2Duo/X38/C2SBX.cfm
	with an areca 1120 with 8*1,5T

It has an Inter em0, as in:
Feb 25 14:46:29 zfs kernel: pci0: <ACPI PCI bus> on pcib0
Feb 25 14:46:29 zfs kernel: em0: <Intel(R) PRO/1000 Network Connection 
6.9.14> p
ort 0x1820-0x183f mem 0xdf900000-0xdf91ffff,0xdf924000-0xdf924fff irq 16 
at devi
ce 25.0 on pci0
Feb 25 14:46:29 zfs kernel: em0: Using MSI interrupt
Feb 25 14:46:29 zfs kernel: em0: [FILTER]
Feb 25 14:46:29 zfs kernel: em0: Ethernet address: 00:30:48:de:97:cd

I runs 8.0-STABLE as of today,
but the same problem is there on a 9 februari kernel.

And just out of the blue it started today locking up the network device.

Everything else seems te work, only pinging out doesn't work.
And the device cannot be pinged from the outside as well.

But I can log in, do work on the system but the ethernet device stays 
offline no matter how hard I prod it.
Sometimes I get the response:
Feb 25 17:41:42 zfs kernel: em0: link state changed to DOWN
Feb 25 17:41:42 zfs kernel: em0: Could not setup receive structures
when I want to UP the device.

Rebooting is the only way out.

So what is going on here????


===============================
BUT there's another snag:
shutdown -r now times out on one or the other daemon.
After which the system no longer tries to reboot, does not respond to 
the keyboard.
So in the end a hard reset is the only way out.

All help welcomed.
--WjW