I recently upgrade to BT5R1 and ran my easy-creds script. Immediately, ettercap gave the old L3 error of not forwarding packets. My first thought was that Ettercap, being so old, was to blame. So I ran the command I had scripted by hand without issue, then I ran urlsnarf & dsniff, no issues.
As soon as I added SSLStrip, the errors started flyign again like crazy. I stopped SSLStrip, they went away. I then fired it back up and went to my victim and attempted to browse to yahoo.com. Again, it was obvious that the packets were not forwarding.
I can confirm I have checked all the "basics" involved in using ettercap & sslstrip. (easy-creds had no problems with BT5 or BT4R2)
That being said, I am not sure if its a kernel issue or SSLStrip. I know that the only thing that has changed is the Kernel. That being said, purehate confirmed the IPTables are not something they mess with.
Anyone have the same experience? Have any ideas?