It happens 100% of the time after a realtime audio export from Cubase.
Not tried without realtime ticked yet, I will give it a go later.

John Reid wrote:

So far, I experienced a crash on exit using the AlphaTrack on Windows 7x64 with 64-bit Cubase 6 the first two or three times I ran it but unplugging the AT before exiting was a workaround.  I've used it for several sessions in the meantime however, and now for some inexplicable reason it is working perfectly all the time.

Same for me, it's intermittent but has not resolved itself.
On closing Cubase6  64bit  I get two Win7 Program has crashed messages, I click close program twice and it closes.
Probably 15% of the time.
Not a show stopper but I know of another person with same issue and it does not happen if Alphatrack is not connected.

Info of crash below --- never sure whether it's useful

  Problem Event Name:    APPCRASH
  Application Name:    Cubase6.exe
  Application Version:
  Application Timestamp:    4cf95e39
  Fault Module Name:    Cubase6.exe
  Fault Module Version:
  Fault Module Timestamp:    4cf95e39
  Exception Code:    c0000005
  Exception Offset:    000000000106baa8
  OS Version:    6.1.7600.
  Locale ID:    2057
  Additional Information 1:    4a73
  Additional Information 2:    4a73ada7b43d800bd2fe8dd7ff008f38
  Additional Information 3:    4147
  Additional Information 4:    4147e0795387dd395b5a5039b2869521

and the second one minus lines that were same as above

    Exception Offset:    0000000000feb9d8
   Additional Information 1:    44c1
  Additional Information 2:    44c11d1e91aa255e6987feda590b6eb7
  Additional Information 3:    46d8
  Additional Information 4:    46d89ea4f39bd5196c25d316fbf75742