unplugging ethernet hangs macbook

If you have anything mounted: Flash Drive, External HD, another computer. You Must Eject it before uplugging your cables.
Most devices are not Hot swappable: The Mac is communicating with it, not actually transfering files but just keeping the connection open.

You can sometimes screw up the file structure of devices/drives by not ejecting them. Ive had to reformat my ipod & an External HD due to this. It only takes a few times before you Permanently remember to eject everything.

There is an easy keystroke: Highlight the Mounted item and press
Command-E to eject. (Apple-E)

i remember that the older versions of OS X caused the beachball alot: If you have 10.4 it usually handles a connection disruption better and recovers much quicker.