where's my admin gone?

I just upgraded to 1.3.9c after a hacking incident. All went well initially, but then I started going through the list of security tips, and somewhere along the line my admin has become a blank page. What could have happened?
It might have been after changing my database username and password (in mySQL DBs and in configure.php) but I'm not sure. Should have been checking after each change, I know.

Not sure if this is relevant, but all my product images have also disappeared from the store.

There's not an easy answer to this.

It's most likely a syntax error causing a fatal PHP error before your site sends anything to the browser. But that could be located anywhere that you made a change.

If you can't remember where you made your changes, then I'd recommend using a file comparison tool such as WinMerge to find the difference between your site as it is now and the backup that you took before your started making the changes.

Hey thanks kuroi, I found a couple of extra 's in <admin/includes/configure.php>, and managed to get it back up again.
But still no images.

That's usually a server configuration issue preventing the images (and often CSS files too) from being sent to visitors' browsers.

I recommend checking with your host what your folder permission should be. Historically they tended to be 777, but nowadays 755 is more usual.

However, some FTP clients still upload as 777 by default, and servers then get uppity with the resulting folders.

But that's really just a stab in the dark.

Yep, I changed the permissions then re-uploaded, and they're displaying now. But this isn't a site that adds new products very often, so I'll change back now. A hacker got into the images file a few days ago - that's the reason for all the upgrading etc.
Thanks for your help.