[TYPO3] FE blank suddenly, BE OK

[Tony Lush]

The front end at http://uscourttennis.org/index.php produces blank pages with no source code. The back end is working and other PHP applications like PHP myAdmin are working fine.

I had been trying to configure the loginbox_macmade, which was not logging in properly. So, after the FE blank pages came up, I rolled back all changes done today to the configuration. After clearing caches, there was still no joy.

TYPO3 4.0.3
TV 1.3

No Apache errors are generated.

Can someone suggest a way to troubleshoot this?

Thank you -- Tony