I think I got it! Found this in Slacker's FAQ:
When I connect the Personal Radio Player to the USB port, I get a message about limited or no connectivity.
The most common cause of this problem is a network conflict. Built into Windows XP and Windows Vista is a program called Internet Connection Sharing. The Personal Radio Players use this program to access the Internet and connect to the Slacker servers. When you use this program, it uses a network address of 192.168.0.1 for the connection. If you have another device on your home network, such as a router or modem (Dsl/Cable) that also uses this same address, then it can cause a conflict. At this time, Microsoft does not allow us the ability to change the address for Internet Connection Sharing. Therefore, in order to resolve the conflict, you would need to consult the manual or manufacturers help on changing the IP address of the device causing the conflict with this address.
Took the plunge and logged into my router and changed it to another number other than .1. Rebootted the router and yipee refresh via usb is happening as I type.
Now all I have to remember is my router login is different...