BUG #14644: Cannot login into the db server

The following bug has been logged on the website:

Bug reference: 14644
Logged by: Nagarajan S
Email address: nagarajan(dot)s5(at)tcs(dot)com
PostgreSQL version: 9.5.3
Operating system: Windows 7 Enterprise
Description:

Hi, I am from Chennai working in TCS, India.
I have recently installed 9.5.3 version of Postgre SQL for our production
purposes.
After installation, when i try to access the default server (localhost
server already preconfigured in PgAdmin3.exe while opening) using the user
postgres and the password postgres it says authentication failure.
Please suggest me how to proceed.
Also there are some issues in the hba editor form present inside
PgAdmin3.exe.
Whenever I select any authentication method while editing the hba_conf file,
some other authentication method gets saved in the edited file (ui shows
the selected method but when viewing the same file in notepad or edit plus
it shows some other authentication method).