Greetings,
Here my two cents opinion. According to my experience most white screen failure are due to syntax error in programs or lack of some server resource (max execution time, memory or max filesize request). I did some hack in version 1.71+(5448) to resolve similar problem in importsurvey.php, maybe it helps here.
First I put following lines in config.php
$cfg_memory_limit = "50M"; // Max script memory in megabytes
$cfg_max_execution_time = "600"; // Max script exec time in seconds
$cfg_max_filesize = "512000"; // Max file upload size in bytes
Then insert at beginning of importsurvey.php
ini_set("memory_limit","$cfg_memory_limit"

;
ini_set("max_execution_time","$cfg_max_execution_time"

;
And modify line 25 from
$buffer = fgets($handle, 56550);
to
$buffer = fgets($handle, $cfg_max_filesize);
Config values should be adjusted according to environment and file size. In my case these value fit most occasion, even a survey with around 250 groups, 350 questions and 2300 answers (290K survey file).
At last....remember those changes in case you upgrade version

!!!