Scratchbox needs vdso disabled, which can be done run-time with 32-bit kernels. With 64-bit kernels, however, this is not possible... until now. A colleague of mine wrote a (hacky) kernel module to do exactly that, it seeks the vdso-flag and writes 0 to it. I helped him with dkms/deb packaging, and now it's available for download.
Note that this does not help with any other annoyances with sbox on 64-bit system, but at least it is something.