I can concur that the forcedeth is unreliable on nvidia based motherboards.
I have a ethernet device that works with forcedeth.
0000:00:0a.0 Bridge: nVidia Corporation CK804 Ethernet Controller (rev a3)
0000:00:0a.0 0680: 10de:0057 (rev a3)
Subsystem: 147b:1c12
Flags: 66MHz, fast devsel, IRQ 11
Memory at fe02f000 (32-bit, non-prefetchable) [size=4K]
I/O ports at fc00 [size=8]
Capabilities: [44] Power Management version 2
It works in that it can actually send and receive packets.
The problems are:
1) one cannot rmmod the forcedeth module. Even after ifdown etc.
2) the machine hangs randomly.
Before someone asks, the MB has no serial port, so no stack trace available.
3) The netconsole fails to function with it.
I have installed a standard PCI based intel ethernet card, and only use
that. Without the forcedeth loaded, no hangs since.
So, although I can confirm that there are certainly problems with the
forcedeth driver, without a serial port, I am at a loss at how I might
help diagnose the problem and fix it.
The only help this email is, is to confirm that if someone is raising
problems with the forcedeth driver, it is most likely to be a truthful
report and if they also have a serial port, they might even be able to
give some good diagnosis output.