Nope, no recent Windows Updates applied.

Network discovery is on.

There's a whole bunch of tunnel adapter bollocks included, which is in the attached file in case it's relevant, along with the wireless adapter output, which is using 192.168.43.x and shouldn't be affecting things?

Windows IP Configuration

   Host Name . . . . . . . . . . . . : Storm
   Primary Dns Suffix  . . . . . . . : 
   Node Type . . . . . . . . . . . . : Mixed
   IP Routing Enabled. . . . . . . . : No
   WINS Proxy Enabled. . . . . . . . : No

Wireless LAN adapter Wireless Network Connection:

[snip]

Ethernet adapter Local Area Connection:

   Connection-specific DNS Suffix  . : 
   Description . . . . . . . . . . . : Realtek PCIe GBE Family Controller
   Physical Address. . . . . . . . . : 00-90-F5-9B-5A-57
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
   Autoconfiguration IPv4 Address. . : 169.254.184.205(Preferred) 
   Subnet Mask . . . . . . . . . . . : 255.255.0.0
   Default Gateway . . . . . . . . . : 
   NetBIOS over Tcpip. . . . . . . . : Disabled
   
[snip]

I setup a WebDAV share and can access that from Windows, though it needs to be mapped to a drive letter and seems ridiculously slow - simply opening a text file can take a couple of seconds. :/

Accessing NFS shares on Windows seems like a minefield, and there's an iSCSI option but that seems to have so much configuration... :&

So if I can't figure out WTF is stopping CIFS connecting then that leaves me with FTP. :'(

Have you tried accessing it from a different Windows pc?

I was accessing it from this Windows PC one a month ago, and it was working perfectly.

Regrettably I don't know of any protocols that possess the appropriate temporal aspect to let me record all the settings and changes made before things got screwed up.

You've got an apipa on the Ethernet connection and a class b subnet, I take it you're using the wireless to connect from the windows machine to the network, it shouldn't make a difference but have you tried disabling the Ethernet adapter?

Nope, the wireless connection goes to the Internet.

The NAS is connected via Ethernet to the same switch as the Windows machine. (The NAS doesn't connect to wifi.)

Can you restore from backup to when it was working?

Only if you can supply me with a time machine so I can go back and create a restore point...

Turned off system restore?

Definitely don't have access to another windows system just to try?

Pretty sure Ant can build you one with a rasberry pi.

Nope, but there's only one restore point - created automatically on Friday evening - so that doesn't help. (Ticked the "Show more" checkbox and nothing else appears. Damned thing.)

I have no other active Windows boxes, and I'm not faffing around finding and swapping the harddrive I took out of my netbook since I'm approximately 5000% certain the NAS is correctly configured and the issue is with this Windows instance.

Does the network interface use DHCP or a static address? Either way, you shouldn't be getting a 169.254 address on the interface, so either check that DHCP is still working, or assign a new address to the interface.

No DHCP server, afaik. I did originally intend to setup DHCP+DNS on my Pi but didn't have time initially and then everything was working with 169.254 so I just left it.

Do you still not have a phone line?

Aye, s'what I was thinking.

Can you connect to anything else on the Ethernet adapter? Config looks a bit... nonstandard.

Don't be shocked.

The network engineer in me thinks that 169.254 should never be used so that it's obvious when they crop up that something is wrong. But then there's at least one example of paid work that I've done which uses them for the wireless access points VLAN. Such a cowboy.

Give it a proper IP address and see if that helps.