Like many others, I was experiencing the "blank pages" problem with versions of Atahualpa above 3.6. The various Suhosin fixes that have been put forward weren't working for me, mainly since my host doesn't have Suhosin installed.
However, I ultimately stumbled upon a a hint in my webhost's PHP help files that led me to a resolution. Specifically the potential for problems in Alternative PHP Cache. Adding the following directive to .htaccess restored the missing content:
Code:
php_flag apc.cache_by_default off
Hopefully this might help some of the people who are still having issues.