Comment 9 for bug 362457

I experience(d) a very similar problem here with Xubuntu 10.04 "Lucid Lynx", 32-bit, Kernel 2.6.32-25, SIS 900 chipset in an Asus A2500D notebook, and therefore I landed here:

The network connection was very slow: Maximum downstream of 40 kByte/s.
Not only "internet", but as well internal traffic was affected.
I was not even able to do 2 ssh connections to this machine at the same time.
The boot options "acpi=off", "nolapic" and "noapic" did not make anything better.

I finally solved the issue by adding "irqpoll" to the boot parameters.

/etc/default/grub:
...
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash irqpoll"
...