That same thing happened to me. The way my Alpha Geek friend explained it to me was that since the hub is hooked up to the broadband network, it's like the other computers hooked to the hub are each subscribers to that network. I dont know all the fancy schmancy technical details but basically the reason they cant see each other is the same reason you cant see your neighbor's computer that is hooked into the same broadband network.
Now, I've found 2 workarounds that work for me
1. Unplug the hub from the uplink to the broadband connection. Go into Start->Run, type 'winipcfg' (no quotes, of course). Find your network card in the list (mine says "PCI Network Adapter"

, select it, and hit 'Release All' once or twice for good measure. Do this on both computers, then restart them. This should remove the hub/network from the broadband network completely. When you're ready to go back to sharing broadband, hook it up, run winipcfg, release, restart.
2. Do #1 above. When you can see the resources shared by the other computers on the network (C drive, etc), right click on that resource, and select Map Network Drive. Pick a drive letter. The drive will now show up in My Computer just like a normal drive. This method has worked for me so far even with my broadband connection hooked up. Hopefully I helped you a little.
PS I need some help from you guys. On my 10mbps network, whether it is sharing broadband or not, from Computer 1 to Computer 2 I get a very acceptable file transfer rate, but from Computer 2 to Computer 1 I get a very very unacceptable rate (somewhere in the vicinity of a 56k modem). Any ideas on how to solve? Thanks!