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The hosting server should give some kind of error message, usually its a 500 error or database not found. When I here you say white screen, I think the word Protector, the module. There are some conditions for which Protector can be optioned to result in blank screen.
I just looked in the preferences for Protector and F5 ddos attack and high crawler loading rate are the only configurable options for blank screen. It is not clear if only the attacking entity gets the white screen, or everyone does, or for how long it persists after an attack.