On May 17th Pedro Valente (and Dreamhost) shared this regarding wp-cache:

My wordpress blog is hosted with Dreamhost and I found this in their support wiki:

If you have “blank pages” in WordPress with wp-cache turned on after you upgrage to PHP 5.1.2 – there is simple fix to solve the problem:-

1. Open wp-cache-phase2.php file* in your favourite text editor
2. Find out wp_cache_ob_end function
3. then inside that function find out line with: ob_end_clean(); (it should be line 219 or about)
4. and finally replace that line with: ob_end_flush();

I had already turned off wp-cache, but this solved my problem of a blank screen on every first load.

Here is the code replacement following the instructions above. It worked for me.

OLD:

ob_end_clean();
if ($new_cache) {
$serial = serialize($meta_object);
wp_cache_writers_entry();
$fr = fopen($cache_path . $meta_file, 'w');
fputs($fr, $serial);
fclose($fr);
wp_cache_writers_exit();
}


NEW:

ob_end_flush();
if ($new_cache) {
$serial = serialize($meta_object);
wp_cache_writers_entry();
$fr = fopen($cache_path . $meta_file, 'w');
fputs($fr, $serial);
fclose($fr);
wp_cache_writers_exit();
}