This actually worked for me .. thanks!I had a similar problem, upgraded to 10.04 from 9.10... rebooted etc., no problems. Today, no internet and no "network connections" icon in panel. I am hard-wired via a router.
* Solved the "network connections" problem by opening "Run Application" (Alt+F2), type and run: "nm-applet --sm-disable". The network connections icon now appears in panel.
* Solved "no internet" issue by clicking on icon and check "enable networking". After a few min, have internet.
Do not know enough of Ubuntu to know if this would help, but that's my $0.02.