I've been using Mprime 2.35 on Libranet 2.7, 2.8 and Slackware 9.0 - kernel versions 2.4.20 and 2.6.4 (which I abandoned because it ran slightly slower) - since last September without any connection problems. (Well, OK, occasionally the server may have been unavailable for a couple of hours.) I've used it over external dial up modem and via ADSL. I've run it through a firewall. I've never had to tweak the settings. (So I'm probably not going to be much help

)
I take it you can use the box for normal internet access so you know it's not just a dodgy cable or card?