I have file sharing enabled in Windows 7 64bit to access files over the local network. I have used it for years to move files to and from my phone (using an File Expert that supports SMB) and access media on my Wii using homebrew.
Yesterday it suddenly stopped working with no apparent cause. I cannot connect to it from either the Wii or File Expert. I do not have another Windows machine available on which to try it, but if I type in the network address on the computer itself (//COMPUTER_NAME or //COMPUTER_IP) it acts like it is working. It seems unlikely that both devices failed at the same time so I'm pretty sure it's the computer. I've tried restarting and running Microsoft's "Incoming Connections" troubleshooter but it did not solve the problem.
I'm not even sure where to look further or what to try.
Edit: This is embarrassing but it turns out the problem is with File Expert. WiiMC defaults to the location you were looking at when it last closed. It seems that means it will bring up the previous message. If I had dismissed it and tried again without restarting the Wii I probably would have noticed it works. So it failed at some point but is not an ongoing problem.
So not fully fixed but now I have a much tighter window of things that could be wrong. (especially given I just updated my Galaxy S3 to Android 4.3 so I even have a clear cause)