Two weeks ago I installed a fresh copy of Ubuntu 8.04 on some rebuilt / upgraded hardware. All seemed to be working fine until last weekend when my outgoing Thunderbird e-mail attachments started timing out. The transfer starts out fast then tapers off until it finally stops after about 128k.

I've also seen something similar using FTP and even loading web pages, though these aren't consistently timing out like uploads attachments.

The system is configured mainly as a desktop. It has two network interfaces. One wireless [802.11g] to the house NAT-Router(s) and on to the Internet. The other wired to my old Ubuntu desktop box. At one point I set up a second NAT-router and ruled out that as a source of the problems.

My housemates haven't noticed any problem other then the generalized "the Internet is slow" reactions.

How do I tell if the problem is local to my machines / network or out in Comcast land somewhere?

Get a download location and do a wget download from your Linuc server, and se what the average transfer rate is

Always good to test more than one site, and then test local and international downloads

Try mtr - it pings around on all your hops to a given address and prints out where the bottlenecks are.

Strange thing is that I had trouble with outgoing email lately,too.Where do you got your account?