if you type Export and see something like this:
declare -x all_proxy="socks://127.0.0.1:22000/"
Most sites assume and tell you to check your .bashrc or /etc/profile /etc/bash.bashrc which may not apply if you've unknowingly or forgot that you setup a proxy from your GUI such as Gnome.
To check in Gnome if you have a permanent proxy do the following:
System -> Settings -> Network Proxy........
I've encountered this problem before and I believe it may affect other drivers (I could test but I don't have time). This was happening on my custom Linux system with the pcnet32 driver.
pcnet32: eth0: transmit timed out, status 97fb, resetting (and some other kernel module tracing in dmesg)
Basically it means the card is connected (it shows connected in full duplex etc.. and recognized if the cable is disconnected too) but no packets can be sent or received........