I've got the exact same problem with the rge driver. I also tried the hardware checksum switch and also didn't have any luck.
I have been trying to get the geni driver up and running instead, but I've also been running into issues with that. The driver installs and attaches to nic without issue. I can ping its own ip successfully, but i cannot ping anything else (this includes ip's on the same subnet). So its not dns, and its not my gateway.... Something isnt right, but cant put my finger on it. i'm back on the rge driver at the moment, and i'm just living with the intermittent network issues. Bit of a pain, but don't really have a solution or fix. A lot of other posts have recommended buying a new intel nic, bypassing the issue. (but of course that costs money) -- This message posted from opensolaris.org