I encounter problems during starting up Ubuntu 12.04 laptop. There is no internet connection (wired network connection is established though) and there is no error message from network manager or other system part.
In the very beginning, email is working but after 2-3 min it is not working anymore.
Other pcs are working (email & internet) without problem. Router shows that internet connection is alive.
After resetting router (and network connection as well), problem disappears till next boot.
Which error or log file should I look in to try resolving the problem?