Weird pop3 problem over wireless connection

[cfl4g]

Please help me out here...I'm going nuts..

Scenario: A home network with one Gentoo server running firewall/router, web server, http proxy (Yeah... I know ) and two laptops behind it.

One of the laptops (mine, also running gentoo) has a weird problem with its wireless connection. When trying to initiate a pop3 connection over it, the initial handshakes go well, but the pop3 banner never appears.

$ telnet xxxx.xxx.xx 110
Trying zzz.yyy.ccc.vvv...
Connected to xxx.xxx.xxx
Escape character is '^]'.

.(Well, actually, sometimes it does about 10-20 seconds later, and then I am actually able to log in and list the messages, except that the responses arrive somewhat skewed i.e.

user xxxx
<no answer>
user xxxx
+OK Password required for xxx
pass xxx
-ERR USER already specified

I thought it looked like a NAT problem, but when I plug it in the wired network, everything's fine, and telnetting from the server/firewall also works fine.
Probably being related, I have also had some problems with the internet connection. It only works if I force it to half duplex / 10Mbit and an MTU of 866 (any higher and nothing gets through). I have also had to manually set the MTU for the wireless interface on my laptop or else nothing gets through there either (have also tested with mtu = 500/1500, still no pop3).

So is this a wireless configuration issue? I mean it basically works, browsing/streaming and all except for receiving mail

Any ideas????

Thnx in advance!