So, I went and bought an Intel Pro server adapter and installed it...
http://www.newegg.com/Product/Product.aspx?Item=N82E16833106114
This is clearly labeled as supported by VMWare in their compatibility list. Exact same results: a combination of packets received and dropped. A comment on the NewEgg page confirms it working in ESXi 4.
The odd thing is, doing a:
lspci -p
shows using PCI ID: 8086:1026
while lspci shows that the chipset is 82545GM. According to the simple map file on vm-help:
http://vm-help.com/esx40i/Hardware_support.php#Intel
this PCI ID belongs to the 8254NXX Gigabit Ethernet Controller chipset. The 82545GM chipset is not listed on this page. Is it possible that I got myself another incompatible card? I kind of doubt it, but I don't know what else it could be.
Again:
1) Both cards work in Ubuntu in the same PCI slot on the same machine
2) I've disabled all hardware not-in-use within the BIOS
3) The card is detected (rightly or wrongly) by ESXi, the machine boots
4) Some packets are being dropped, I cannot connect via vSphere Client
Because I'm experiencing the exact same problem I'm tempted to think that this might be something hardware related with my PC, but I can't think of what this might be...
Any ideas?