For those with the SPB calculator issues, please make sure you have the correct registry key below. Odds are that you don't and this is being fixed for the next update.
Code:
[HKEY_LOCAL_MACHINE\Software\Microsoft\Shell\Rai\:MSCALC]
"0"="Calculator"
"1"="calculator.exe"
"2"=dword:2
"3"=dword:0
Edit: well, this may not actually be the cause, but its good to check the registry key anyway.