Look under connection information for the connection you use to access the net. If the driver is r8169 and you have a Realtek RTL8111 network chip on your motherboard then follow this post to get the correct driver installed. Ubuntu 11.10 uses kernel version 3.x so take the necessary steps noted for this kernel version (I didn't modify the makefile, just copied the files as instructed instead).
To find out what network chip you have try running
lspci to list devices on your PCI bus. The culprit was
05:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 06)
Before doing this my internet connection was inconsistent, slow and would drop a lot of packets (as shown by running
ifconfig). Now its running fast with no dropped packets.
Point taken about my post being "forum like" in the comment, I have amended this answer to reflect that.