Question: So, I've been using the new(ish) Bash on Ubuntu on Windows (WSL) for a while now and all has been top-notch, until yesterday. 

I git-pushed from Bash by accident, so it asked me for my repo-destination account details like normal. I decided to ignore this, terminate Bash and try to just use powershell instead (can't ever remember passwords!). Terminating Bash however caused the shell to freeze. I forced closed and restarted my comp (I've had to force close and restart several times before for various reasons and everything was fine).

After boot up, I just tried to check if Bash was working again, but it wasn't. It just failed to start with no error message. For example:

```
PS C:\WINDOWS\system32> bash
PS C:\WINDOWS\system32>

```

Has anyone else had a similar situation/knows how to help?

EDIT: Only solved through reinstalling bash, using

```
    lxrun /uninstall /full

```

then 

```
    lxrun /install 

```

Answer: 
Came here with a similar issue, but a different solution, so I'll post in case it helps anyone else.

The difference in my situation was that, when running `bash` through Command Prompt, it complained about Legacy Mode being enabled.

1. Open a regular command prompt (`win+r` then `cmd`)
2. Right-click the title bar and select `Properties`
3. Deselect "Use legacy console (requires restart)"

Now it should work either by launching the standalone app, or typing `bash` into a regular `cmd` window after restarting Command Prompt.

This and other causes can be found in [this Github issue](https://github.com/Microsoft/BashOnWindows/issues/849).
Right after Windows Updates KBB4471324 and a reboot, Bash wouldn't launch. No messages.

In event viewer I saw messages about 

> 
> The application-specific permission settings do not grant Local Activation permission for the COM Server application with CLSID
> 
> 
> 

I didn't bother trying to figure out if the SID, CLSID and APPID were associated with bash.

I launched Bash as administrator, which worked, and then bash as a normal user, which worked.
It seems to be fine, now.