WSOD (white screen of death) can happen in drupal for different reasons. One is that you could be missing some files, probably modules. Maybe you moved something wrong when migrating, or you have wrong git branch or just delete module(s). Anyway when module is missing drupal will try to find it like crayze For example: 1 missing module lead to 900 file_scan_directory() calls resulting in a wasted 250ms every page load it is said here
https://drupal.org/project/missing_module on this missing module page. This problem has also been reported and talked about here http://timonweb.com/advice-may-help-you-if-your-drupal-7-has-started-ru… and it is an issue still not resolved here https://drupal.org/node/1081266 So anyway with above links you have tools to make this work. You can try to find missing modules by looking at DB system table and fill them in, or disable all the modules, then add module above and then fix what is missing. Anyway good luck. (also maybe try some of the patches in that issue queue).