Question : Vista file sharing across an Access Point / Network merging, etc.

I have a simple LAN that includes a wireless access point device.  
Some computers are wired and some computers are connected via the AP / wireless.
All computers are on the same subnet as you might well expect.
Most computers are XP Pro.

We just introduced a new Vista system on the wireless  part of the LAN.
The Network and Sharing Center settings were normal for our Vista systems:
  "private network,
Network Discovery ON,
File Sharing ON,
Public Folder Sharing ON,
Printer Sharing ON,
Password Protected Sharing OFF,
Media Sharing OFF.

We shared the C: drive and the following observations were made:
All the computers on the LAN could see and get into the Public Folder
Only the wireless connected computers could see and get into the shared C: drive.
The wired computers could see but could NOT get into the shared C: drive ... initially.

I notice in other LANs that the wired computers in Network and Sharing Center are connected to "Network"
I notice that this wireless Vista computer in Network and Sharing Center is connected to "[ssid]" as a network name - so I suspect that a wired Vista system on this same LAN would be connected to "Network".

I found the control that will "merge" networks and merged the SSID-named wireless network with the "Network".  That didn't help.
I added Everyone to the permissions on the Vista shared drive.  That didn't help.

Eventually, I added Guest to the shared drive permissions and it fixed the problem.  Now all the computers on the LAN can see the shared C: drive and can get into it.  
On other LANs I've not had to add Guest in order to gain access to shared folders such as c:\Users\Me

I wonder why having the wireless segment matters here?
I wonder if the C: drive is handled differently than a subordinate folder in such a case?

I need explanations that will allow me to reliably network Vista machines!

Answer : Vista file sharing across an Access Point / Network merging, etc.

I've had the same issue with Vista when sharing drive roots (e.g. the whole drive).   Adding the Guest account and "Everyone" always resolves it.   I've seen this on both wireless and wired nodes, however, so it's not clear that it's just a wireless issue.   As I think a bit about it, however, the wired cases were always going through an extra switch (which should NOT have any bearing on it ... but is just one more piece of the network topology involved).

I've not had the problem with subordinate folders;  so I think it's just an issue when sharing the drive's root.   Are you SURE you've had different behavior with wired vs. wireless?   ... or the previous cases not involve sharing the root?