Once you changed your domain's password, the SourceTree will ask for password once. You typed in the new password and it keeps asking for it. If you hit cancel, it will be able to use all the related repos. However, it will:

1. Randomly pops up a window asking you for password again and again even you did nothing on the SourceTree; And / or,
2. Lockout the AD account silently after you clicked the cancel button and let it stay there for a while. (Yes, after cancelling it, it will allow you to use all the related repos! Fetch, pull, push ... everything works)

Today, I got my account locked out again. After asking IT guys to unlock my account for thousands of times, I finally couldn't take it any more. And I went out there to search if there is any solution. And I got this:

https://answers.atlassian.com/questions/22653861/sourcetree-keep-asking-password-windows-8.1

In this ticket, Balazs Szakmary gave a clue about the authentication in Tools\Options\Authentication. I went there and deleted the old password. Now, things went even wrong from already wrong:

1. When I tried to use the related Repos, it just complained failed to authenticate but not pop up window to enter the password.
2. There is no way to add a password in the Tools\Options\Authentication window. I have to quit and reopen the SourceTree.
3. After doing so, it popped up the window for asking password. However, after I typed in the right password, it kept complaining authentication failed.
4. Now, I cannot use these related Repos any more even if I clicked cancel button when it asking me for password.
5. Well, just like before, I did nothing but left the SourceTree out there in the corner, not touching it. And it would suddenly pop up a window asking for the password for no reason. And no doubt, it failed to login even if I typed in the right password.

I tried uninstall the SourceTree and reinstall it again couple of months ago. And it seems to be working. However, I don't believe this is the right way to use a software. And I thought I tried remove the book marks and it didn't work.

Update1:

Just before I start trying to uninstall and reinstall as I did the last time, it went back to the point which and access the Repos but still pops up window asking for password suddenly and randomly. What I did was nothing but open it, close it, and re-opening it. And I did remember I tried typing my password and it did asking me again about the password as usual. And I again cancelled it but I can't remember what next I did. Maybe I just closed and re-open it. However, it's still not behaving normal.