I thought I would post this in case others were having issues with Joomla 1.5 showing a blank homepage. Apparently my hosting provider upgraded their PHP from 5.2.17 to a 5.3 version. When they did it was causing incompatibility issues with all my Joomla 1.5 sites. I could access the back-end admin area, but could not preview the site publicly.
For those having these same issues, the fix is basically a core code change in two places...
Line 31 of the helper.php file under /modules/mod_mainmenu remove the & (ampersand)
open the /public_html/libraries/joomla/html/html.php
and find the (line 87) :
return call_user_func_array( array( $className, $func ), $args );
put & (ampersand) sign before the $args :
return call_user_func_array( array( $className, $func ), &$args );
If your helper file does not have the & (ampersand), then you are probably not experiencing any compatibility issues.
I'm researching further to see if this also has any effect when migrating DTR in Joomla 1.5, using PHP 5.3.