I have experienced most strange thing in Ubuntu last day. I have a Dell latitude laptop which i used in India with ubuntu 10.04 and windows 7 installed in it. I could connect to internet by using both wired and wireless interface in both os. Now i moved to France and have done nothing to it, but now i couldn't see any network interface in my ubuntu for both wired and wireless. Any idea?
Well, for Wireless you might have disabled it by the switch or a key combination. Try enabling it. If it doesn't work in Ubuntu, try it in Windows and restart to Ubuntu. Also check if it is disabled in the BIOS.
For wired, either Ubuntu tried to update the LAN driver and failed rendering that card invisible, or it is disabled in BIOS. If you know the model of the card (eg Realtek RTL-8111F) try at manufacturer's site for latest Linux driver. If I remember correctly, for Ubuntu you download the .deb version, if available. Of course you should download the 32-bit version for 32-bit Ubuntu and the 64-bit version for 64-bit Ubuntu. If lucky, by reinstalling the LAN driver, the card should come back to life.
I don't know about Ubuntu, but a utility for Windows to see which hardware components you have in a computer is former Everest, newer Aida64. It can tell you with detail even if no drivers are installed. This is useful if you face an unknown machine, so you know which drivers to download. At worst case you can see the vendor ID and device ID, Google it and find out which device is that. If you cannot find drivers at manufacturer's site, one good one is www.driverguide.com Be careful though as it may try installing unwanted software to give you the driver for free.