I have the same issue (blank screen) with CMS Workflow (rc2, rc3, and trunk-r101776).
silverstripe-v2.4.0-beta2 + genericdataadmin-trunk-r91391 + subsites-trunk-r101755
Errors from the apache logs:
PHP Fatal error: Class 'PopupDateTimeField' not found in ... /BatchSetEmbargo.php
CMS Workflow looks like it prefers TZDateTimeField and defaults back to PopupDateTimeField, neither of which exist in 2.4.0-beta2.
Tried Latest Daily (silverstripe.2.0.DailyBuild.2010-03-30) but that won't even let me run dev/build.
Based on errors in the apache error log, I copied the following from the Daily back into 2.4.0-beta2:
Flat specified but can't find parent.
$.concrete is not a function
this.icon is null
$("Form_EditorToolbarImageForm").respondToNodeChange is not a function