if you have a nic thats not working properly, be sure to check your interface confirmations to make sure you either have it on half duplex or full duplex

you can use the mii-tool command, like this for example on eth0

mii-tool -v eth0

this is the output looks like:

eth0: negotiated 100baseTx-FD flow-control, link ok
product info: vendor 00:08:18, model 22 rev 2
basic mode: autonegotiation enabled
basic status: autonegotiation complete, link ok
capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control
link partner: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control