I have faced this issue mostly in Fedora (both 9 & 10). When I start Firefox, it starts in offline mode. I had to manually change it to online mode (File-> Offline Mode [uncheck]). Today I became frustrated. But after searching net for a while I found some solutions. After testing all, I found the real solution.
- Open new tab in firefox
- type about:config
- Click I’ll be careful, I promise
- type networkmanager in Filter box and press Enter
- It will show preference name below. The last column (Value) should be true. If not, double click on it. It means, you need to set toolkit.networkmanager.disable as true.
That’s it. Restart your browser. It should now start online mode.