Pekka Niiranen wrote: > However, using > highbits=0x7fff0000 # equals hex(sys.maxint) > gives no errors, but does locking work if > highbits are not exactly 0xffff0000? Try using highbits=-0x7fff0000 as your mask. That should set the MSB without tripping over the sys.maxint limit. Cheers, Nick.