I don't know what te issue is. Yes, it could be a problem in 5.0.1, but I have not seen it on my 5.0.1 (maybe I'm not running long enough though, although I was thinking it happened in just a few minutes). BUt it does seem more likely an issue with your network, and the 255.255.255.255 broadcast address really throws me. You might want to look at the router setup and see if these are user settable settngs that might have been screwed up. I would also uggest looking to see if there is a newer firmware version that you could download and flash the router with.

Yes, I hope you are the only person on your router. As long as it doesn't have wireless capability and your systems have not been taken over by an evil hacker I expect that is the case.

Sorry, I don't have any one good source for networking information. But you can find links to all you need and more at Google. For example this simple search will give plenty of links that help you understand broadcast addresses and should help you see why your 255.255.255.255 address makes no sense to me. But be warned, you just can't trust everything you read on the Internet. In this case the very first link that I got with the search (your links may be different, Google is funny that way) was www.net.princeton.edu/iprouters and it's information is dead wrong! Broadcast addresses must never end in zero as it shows them doing. But the second link that I got was www.tldp.org/HOWTO/archived/IP-Subnetworking/IP-Subnetworking-3 and it gives a much better (and correct) description of the broadcast address. I expect that you could learn a lot just by starting at any network term in Wikipedia and reading the article and following links. And here is a good one on the broadcast address to start with. If you read nothing else I give in links, read this. Also, it would be good to learn to read and use the RFC's and fall back to them when you have a question on how things work.

Back to the problem, I'm running out of ideas. You could say it is maybe a bug in 5.0.1, but that doesn't help you and may not help get a bug fixed if there is one. The best thing that I can think of doing (if there is no firmware update that fixes this), would be to watch the packets with ethereal and see what is happening as things break down. Are you still seeing your requests go out? Do you get any sort of responses? Can you do other things like simple pings when things start falling apart? What has been happening on ARP while all of this goes on? Do you still see ARP packets at regular intervals as the systems announce themselves and try to keep the router tables current? (hint: do this for a while with 4.0.2 and/or Windows so that you can watch a functioning system and get a feel for how ARP works before you watch it go to hell with 5.0.1). If you can find and document a bug with 5.0.1 then that gives you a much better chance to report it and get it fixed in the next release than to just hope that someone else does it (someone else doesn't have your router with the wacky broadcast address).