403 Forbidden error – index.php 000 permission

I just checked what was a perfectly healthy website (at least last week it was ok). Today I am getting this error –

Forbidden

You don’t have permission to access /index.php on this server.

Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request.

I looked at my site and found that the index.php is 000 in permission. Tried to change it using file manager to 644 but I cannot change permissions. In the CPanel File Manager, it seems I am able to change permission to 644 but when I move around to another directory, and come back to the main WP directory, I see the index.php is back at 000 permission.

My .htaccess file reads like this (I have WP-Padlock installed)

<Files 403.shtml>
order allow,deny
allow from all
</Files>

deny from 62.139.191.1/32
deny from 62.139.191.2/31
deny from 62.139.191.4/30
deny from 62.139.191.8/29
deny from 62.139.191.16/28
deny from 62.139.191.32/27
deny from 62.139.191.64/26
deny from 62.139.191.128/26
deny from 62.139.191.192/27
deny from 62.139.191.224/28
deny from 62.139.191.240/29
deny from 62.139.191.248/30
deny from 62.139.191.252/31
deny from 62.139.191.254/32

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

The IP addresses (probably from a hacking attempt) do not match my ip address nor my hosting ip address.

Just previous to this issue, I upgraded to 3.2.1 and my left side navigation bar went out. I followed the procedure and got the left nav bar issue fixed.

Luckily, I am able to get in the wp-admin. I started turning plugins on and off but no success so far.

Anybody else having this problem? Please advise…