Bizarre Transmission-induced network bug, driver crapping out maybe?

[Chris Neary]

Guys, I think I solved it. I should have mentioned that
network-manager, if it's still called that these days is saying
'device not managed' for my sis190 eth0 device.
I bought a £6 PCI NIC today, and it works beautifully. Torrents are
downloading quickly and seeding well. Bizarrely, while my torrents
worked at a crawl plugged directly into my modem, I had minimal web
access: Only Google would load (from Firefox and even w3m!); even
stable sites like bbc.co.uk were inaccessible, and would halt at
'Waiting for (server domain)...'

SIS are useless. Onboard graphics flickered, onboard sound had
crackling interference. Onboard network close to useless. AVOID at all
costs. :)

Thanks for helping anyway, but this time it turns out to be dodgy hardware. :)