Indeed, that looks like a bug. It should be fixed on trunk now:
> I think I found an error when JSONValue is called on an empty string.
> The debugger reported this error: Program received signal:
> “EXC_BAD_ACCESS”.
> Look in SBJSON.m on line 312 in objectWithString:allowScalar:error:.
> When err2 is not nil then o will be undefined and will fail on line
> 319 in the call to isKindOfClass. This method should return nil
> without an error if repr is an empty string.
> Has anyone else noticed this?
> Larry
Stig