Wireless Networking Problem Making Me CRAZY!

We have four PCs: one running Windows 98SE, two running Windows XP, and one running Windows 7 [Home Premium]. Until recently they could all see one and other as well as share files with each other. Recently I discovered they could all still see each other and the two XPs and the Win 7 could connect with each other. They can also connect with the "98 machine" while it can ONLY connect with the two XPs When I try to connect with the Win 7 PC via Windows Explorer or Network Neighborhood I receive the following:

\\ [pc name] is not accessible

The request is not supported by the network

When I click on properties for Win 7 (while on the Win 98 PC) I recieve this message:

The server \\ [pc name] does not accept remote requests

Info for the Windows 7 PC:

OS: Windows 7 Home Premium
Service Pack 1
Processor: Intel(R) Core(TM) i5 CPU 650 @ 3.20 GHz
Installed Memory (RAM): 8.00 GB (7.89 GB usable)
System Type: 64-bit Operating System

System Properties
Remote tab
Remote Assistance
"Allow Remote Assistance connections to this computer" IS CHECKED

If you need more information, just say the word. But I have to warn you, I'm not what one would call "computer-savvy" but I try my best.

Thanks for any and all help,
Chuck W