My site suddenly appears blank

See if you can log in with this: http://www.sagud.com/wp-login.php

If it looks like you logged in, but takes you to a blank page afterwards,
try this in your address bar: http://www.sagud.com/wp-admin/themes.php
or http://www.sagud.com/wp-admin/options.php

One of those might get you somewhere, or it might not.

I see you’ve uploaded the WP 3.2.1 files, but your last cached pages
( ~ Nov 28) says you were using WordPress 3.0.1. You shouldn’t rule out the possibility of a compromise, if you have made no changes yourself.

I can access all those URLs when I’m logged in.

So, what does that mean? Are you saying that you can access and see your themes page after logging in?

What’s the problem with the changing a version?

There’s no problem with changing a version… Unless you were compromised before you upgraded. Upgrading after you’ve been hacked (that’s if you even have been hacked) won’t fix a thing.

Bottom line: Google says that on November 28, you were using a version of WordPress known to be exploitable. – 3.0.1

You said: “I didn’t change anything in my wordpress last 4 months.”

There was a minor security release available on Nov 30. http://wordpress.org/news/2010/11/wordpress-3-0-2/ , however; there has been approximately 12 WordPress security and upgrade releases since version 3.0.1.

I’m simply saying that it’s possible that:

a) you could have been hacked,
b) you did not keep up with security and update releases, and
c) your statement that you have not made any changes in 4 months, sort of lends support to the idea that “someone else” could have.

…Or, it could be totally unrelated. /wp-admin seems to work, so maybe there is just an issue with corrupted files in your WordPress root directory, or perhaps the theme directory.

I can access all /wp-admin/ “things”, but can’t access real site.

Have you tried changing to a different theme, or disabling any plugins yet?

This might be a clue- //www.sagud.com/wp-admin/install.php

I would normally expect the install page to return this message:

“Already Installed
You appear to have already installed WordPress. To reinstall please clear your old database tables first.”

You may want to contact your host and see if they have any thoughts on why you are getting this 500 error.