Vista - Seeing other computers on a wireless router network.

I have a dlink wireless router with a Dell M1530 laptop and a XPS 420 desktop. After a lot of help from Dell, I set up the home network which was working fine. I even set up some network drives to look at and transfer files between machines. Now, the network seems to act strangely. Most of the time, the other machines mapped drives show up with the red X and can't get connected. The network connections don't show the other machine but an IP scanner will sometimes see them. I even used the IP scanner program to transfer files between machines even though they supposedly were not connected.

After the trouble I had getting the network set up, I hate to try to set it up again. The internet access to both machines works fine. I have all hard drives set to share. I use WEP security.