OpenSSH connection trouble

I'm trying to use Putty 0.60 to log in to an OpenSSH 5.3 server. Connections with openssh from another Linux server are possible, but Putty fails. Putty's event log tells me "software caused connection abort" right after the DH key exchange, the server log doesn't report anything (set to INFO). I analyzed the traffic with Wireshark and got a whole bunch of "TCP retransmission" and "TCP DUP ACK" after said key exchange. Sometimes I was able to log in, but at some point (usually < 2 min.) the connection froze without any logged messages. Sadly, I didn't capture a trace.

The serv开发者_运维知识库er is my own (Funtoo with genkernel and gentoo-sources 2.6.34), so I may tweak it, but I'd still like to know what causes the error. Any suggestions? Thank you!

Ok, that was weird.

The problems cause was a network BIOS setting: a specified static IP and NIC = shared (Broadcom Extreme II) - system in question is a Dell Blade. By these settings, I somehow ended up with multiple MAC addresses for the IP - which killed my SSH connections. I honestly hope this helps somebody else...