The computer in question is a Dell Vostro 1500 laptop. It started out running Windows Vista Basic. It was later (a few years ago) upgraded to Windows Vista Business. It was subsequently upgraded to Windows 7 Pro.
The problem is that when connected to our wireless router, a Cisco Small Business RV 120W over the wireless network, I am unable to connect to other computers on the network running either Windows 7 (no Homegroups have been set up) or Windows XP Pro, with the exception of our file server which is running Windows Server 2003. However, when I disconnect from the router, and connect to our wireless access point (set up at the other end of the office to extend the wifi range) I am able to browse the network neighborhood and to connect to printers and shared folders without any problems. I am also able to browse the network neighborhood and connect to shared printers and folders when connected to the Cisco router via a wired Ethernet connection.
The wifi access point (a LinkSys WAP54G) has it's own SSID, but uses the same WAP key as the main wifi network (to keep things simple as far as the initial connection to the wifi network is concerned.)
The problem browsing the network when connected to the main wifi network occurs whether the laptop in question is in the normal room it's used it (a few rooms away from the room where the Cisco router is set up), or whether it's in the same room, within a few feet of said Cisco router. Yet, the laptop in question can browse the network and connect to shared printers and folders when connected to the wireless access point that is at the opposite end of our office (a dental office) from the laptop, with the resultant weaker wifi signal. Even with the weaker signal, I can still do all the normal network-related stuff when connected to the WAP.
When the desired network resource (printers, etc.) is directly connected to the network (i.e., has its own IP address), I can connect to those printers and print to them with no troubles. Right now, the laptop in question is able to print to both our Brother laser printer (serving as its own print server via Ethernet), as well as a wifi-enabled inkjet photo printer, even when connected to the Cisco router via its wifi connection.
The only other pertinent fact I can think of is that the SSID for the primary and secondary networks are similar in name. The main wifi network's SSID is in the form of: JXXXXN_NET, and the secondary wifi network's SSID is in the form of: JXXXXN2_NET.
Any suggestions for things I may have missed, or steps to take are welcome.
I had thought about the possibility of rebooting the Cisco, but have not done that yet, as we're in the middle of our day here, and I will have to wait until no one is using the network to reboot the router.
Finally, this computer *has* been able to browse said wifi network in the past. It is just unable to do so now.