Can anyone tell me if any viruses or malware can disable a network card.. if so what are my options

Malware can do absolutely anything ....... the first thing you need to do is ensure the machine is cleaned, before trying to repair/re-install the NIC.

http://www.malwarebytes.org/forums/index.php?showtopic=9573

Can you enable it again, and if so, does it stay enabled?

This assumes you use Windows XP (I forget the name of the menus and applet for your connections in Windows Vista, as I only use it occasionally, and don't install it at home):

1. Click "Start > Control Panel"
2. Double-click "Network Connections"
3. Depending on the type of connection, you should see something like "Local Area Connection (disabled)"
4. If the connection is disabled, right-click it
5. Click "Enable" in the pop-up menu

If you want to give yourself a connection-status icon in the Notification Area of your Taskbar:

1. In, the same Network Connections applet, right-click the connection
2. Select "Properties"
3. On the "General" tab, check these two boxes:
   
   • Show icon in notification area when connected
     
   • Notify me when this connection has limited or no connectivity
4. Click "Ok"

Reboot and see if it stays enabled. That said, you might want to do some scans, anyway. Not all malware causes computer slowdowns!