Cannot browse LAN

[#1]

Can anybody help, please? I recently removed a virus from one of the computers connected to my home network (of four, all connected wirelessly). Since then, although I can "see" my network drive (a Buffalo Likkstation Live) from the affected system, most attempts to access it via Windows Explorer cause the system to hang, but occasionally I can use it briefly, before the system hangs. I can ping the NAS device and I have checked the wireless adapter has the correct IP address for the device. I can use the system to "surf" the internet. The remaining three computers can access the device with no problems.
I have reinstalled the wireless adapter software and looked for an up-to-date driver (none found). I have reinstalled and updated the Buffalo software. I have used several Microsoft suggestions to troubleshoot the system, to no avail. I have "power-cycled" everything on the network, to no avail.
To transfer anything reliably at the moment, I have to copy everything to a USB key, take that with me to another computer, then transfer it to the network drive and vice versa. Defeats the object really. 
All ideas / solutions appreciated.

[#2]

What was the virus as this may give us a clue?
Can you connect to another pc ok or is it all network connections?
you can try running from a cmd prompt
netsh int ip reset c:\tcpiprebuild.log
Make sure you know what your network connections are before running this a you may need to add dns etc after its run

[#3]

Have you re-enabled fire and printer sharing (try running the network set-up wizard if it's an Xp machine)? 
Is any firewall on the PC set to allow local access (i.e. have you put your local network in the "trusted zone")?  Make sure that you're also only running one firewall and, if you've got Norton or another 3rd party firewall, that the Windows firewall is disabled.  (Does turning off the firewall allow you to access your network?)
Are all the machines in the same workgroup?  Check that the workgroup name is the same as on your other PCs (for Xp right click on My Computer select properties and then hit the Computer Name tab).
Just a few thoughts!!
My first port of call would be the firewall (or any other security software you've got).  As I suggested above, try *temporarily* disabling any firewall (including the Windows built in firewall) and see if you access the network.  You may also need to try *temporarily* disabling your AV (don't surf the web at this point, just try to access your network drive).
If disabling the firewall works you'll need to add your network to the trusted zone (it may be called something else dependent on your firewall software).

[#4]

@Samuria
Thanks, but no change after that. I forgot the name of the virus, but it was one that had affected my workplace over the Christmas holiday (no, I don't transfer data out, or in from work). They replaced M****e with K*******y and I have followed suit!
I can connect to other PC's on the network, it is only the NAS device that presents problems to this one PC; I have checked that all account access rights are identical on the NAS accounts.
@Paul03
You assume correctly, that I am running Windows XP. Sorry, I should have mentioned that originally. Yes, I have re-run the Network Setup Wizard and I can print quite happily to the network printer too. I disabled my AV and Firewall software and placed the affected PC in the "demilitarized zone" of my router firewall; no success. The machines are all in the same workgroup; I've pored over every parameter I can think of to determine what, if anything, is different about this machine.
What is most perplexing is that, occasionally, I can access the NAS drive for a short while, say to edit an Excel spreadsheet, but the PC hangs if I try to open another file. Hence this topic. 

[#5]

Try googilng for winsockfix.exe and run that, it has been known to fix virus affected pc's like this one.

[#6]

the winsock fix is what i posted
netsh int ip reset c:\tcpiprebuild.log or get a util to do it from
http://www.softpedia.com/get/Tweak/Network-Tweak/WinSockFix.shtml

[#7]

Quote from: Samuria

the winsock fix is what i posted

Ahh I have never used it, moved over to Linix a couple of years ago  ;D, but a mate mentioned he used that to fix a couple of machines 

[#8]

Unless you want the PC to get another virus I'd remove it from the DMZ or at least re-activate the Windows firewall.
The DMZ will only help with access TO the computer from outside your network. It will not help access from your computer within the network, and in fact may hinder it. It is usually preferable to use port forwarding rather than place computers in the DMZ if these are known (although this isn't relevant to your case).

[#9]

Hi,
It might be that the new AV product also incorporates a built-in firewall.
I had exactly the same problem when I moved from Symantec 10.x to Symantec endpoint protection v11.  The new version included a firewall which did not allow the LPX protocol by default.
You need to allow the LPX protocol which is the one used to communicate with a NAS device. 
Ping uses the ICMP protocol, so it's common that ping works but the real protocol doesn't.  A successful ping proves that the IP address is reachable, but does not necessarily mean that the protocol (or port) you need is allowed by the firewall.