Computer not accessible

I'm running 2 vista machines. I've always shared my epson printer on these 2 computers. Computer A has the printer connected to it. Computer B has always accessed the printer over the network. But now I can't connect to Computer A from Computer B. I've always gone into the Network and Sharing Center on Computer B, double clicked the network icon, double clicked the Computer A icon, then double clicked on the printer icon to access it. Now when I try to double click on the Computer A icon, I get the message: "\\computer a is not accessible. You might not have permission to use this network resource. Contact the administrator of this server to find out if you have access permissions. The network is not present or not started. For more info, press help." I haven't made any changes to either computer, but I now have an icon labeled "Microsoft Publication Service Device Host" along with the name of Computer A and the Linksys router. This wasn't there before the last update. If I double click on the icon, it just takes me to Microsoft's home page. Anyway, here are the network settings on Computer A:
Private Network
Network Discovery: On
File Sharing: On
Public Folder Sharing: On (read only)
Printer Sharing: On
Password Protection Sharing: Off
Media Sharing: Off

Network settings on Computer B are the same as Computer A except next to File Sharing it says Custom. I've clicked on the "turn on file sharing" option and clicked apply, but it still says custom.

I hope this all makes sense and I really appreciate any help. It's driving me crazy!

Thanks!