The binary and hex string specifiers are case sensitive; can't really see any reason why they should be, and I can think of at least one reason why not: to be more consistent with the numerical specifiers: 0b, 0x, 0B, 0X, etc all work.
contents of ex.err (for one, the other is similiar)
<0117>:: Not expecting to see 'a character string' here
ex = B"1 10 11_0100 01010110_01111000"
^
Press Enter
code 'snipplets' that cause the error
object ex
ex = b"1 10 11_0100 01010110_01111000"
ex = B"1 10 11_0100 01010110_01111000"
object ex
ex = x""
ex = X"1 2 34 5678_AbC"
bugreport.ex output
Version
----------------------------
4.0.5 development (5743:62d94559f849, 2012-10-15 09:43:49)
Operating System
----------------------------
Platform: Linux, Build: wotsit, 3.2.0-4-486:0
Include Directories
----------------------------
1: /home/user/bin/euphoria/include/
2: /home/user/downloads
3: /home/user/bin/euphoria/include
EUDIR
----------------------------
/home/user/bin/euphoria
PATH
----------------------------
/home/user/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/home/user/bin/euphoria/bin:/home/user/scripts:.