For the first one, when you plug in the Linksys, do a dmesg and check the last couple of lines of output. There should be indication of the linksys being detected on the USB bus. From there you should be able to setup the driver for it, although I am not sure what the driver name actually is.
For the sound issue, there is a sound monitor on one of the toolbars in Gnome, though I am not sure where it is. If you get rid of it (or simply delete the toolbar itself and start with fresh ones) this message will go away.