I am certainly not a guru, so from my noob point of view I would ask: Are the following registry keys set?
With PS/2 keyboards, you must enable the keyboard-initiated crash in the registry. In the registry key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\i8042prt\Parameters, create a value named CrashOnCtrlScroll, and set it equal to a REG_DWORD value of 0x01.
With USB keyboards, you must enable the keyboard-initiated crash in the registry. In the registry key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\kbdhid\Parameters, create a value named CrashOnCtrlScroll, and set it equal to a REG_DWORD value of 0x01.
Not only can this be caused by someone manually generating a crash using the keyboard combo, as Shintaro rightly stated, but drivers can force BSODs as well for whatever (dubious) reason through this method, in order to give a notice that something bad has happened with em internally and they need to crash Windows to get you to notice. In fact, taking gander at the callstack:
It's rare cuz, really, drivers themselves should not be calling KeBugCheckEx because they have an issue. They should go through normal channels for exception handling. Instead they use a deprecated bugcheck (0xDEADDEAD was the old manual crash, now it's 0xE2) to perform the task. It's shoddy programming.