When I left my computer it was downloading a game(TF2) and I had my friend list open, the game was downloading well, I surely had internet connection.
After a while my internet adapter was disconnected from the computer, so I had no internet connection.
Steam also tells me so, by the usual messages in the bottom of every window and the message in the Friends window.
When I inserted my adapter again, I had internet connection again and the game started to download again.
I could see that by the info in the Downloads section of the library, which was open all the time.
But Steam still thought I had no connection, the message in the bottom of the window continued to warn me and I had no connection to the Steam network(Friend list).Here's a screenshot[dl.dropbox.com]
I don't think it's related to the bug, but I'm running (X)Ubuntu 12.10 64bit.
I will try to reproduce this bug, did someone else also have this problem?