I've run into a stinker of a problem (for me at least).
I'm using an Acer TravelMate 2423WXMi and just upgraded to LM14 (with Cinnamon) but can no longer update, look at websites, search, download package updates etc. but I'm seeing that my wireless has connected. It's not a router issue as I'm connected to the same router via wireless on another computer and I've also tried connecting to an eduroam network I can and have in the past accessed. I've also just tested the ethernet and that gives the same results.
Diagnosis? Are there any more details I can give you? considering I can't realistically copy and paste Terminal outputs...