Ok first of all, if it is a plug and play nic...
then when you plug it in it might say "new hardware found"
and you will see a little green arrow in your system icon tray for plug and play removable system resources....
If thats the case... its as simple as you cant just unplug it...
you have to "safely remove" that item from your PC
To do that, you right-click on the green arrow and a pop-up should come up with a few options. One of those is Stop. when you click the Stop, it should give you a message like: "it is now safe to remove your hardware" and THEN you can remove it... if you remove it before doing this you can easily fix it by doing a systems restart with the card out... and after you get back to your desktop you can reinstall the card...
the biggest thing is, you CANT remove it, if it is one of those "finicky" PnP devices..
many other items such as USB thumb drives, micro drives, and memory cards are the same way. I have the micro drive for my camera, and If I remove it by just unplugging it sometimes it completely locks up my system
Ok dapper your turn, try a restart, wait til you are logged in on your desktop, and THEN plug your nic in and see if you still get the unstable connection.
also see if you can see the PnP icon I am reffering to in your system tray in the bottom right hand corner of your screen
Mike A!