Please see / discuss in thread "Monted 00 Partitions" <- nice typo there by the way. Problem reported is NOT bitstream related but SD card. Always (quick) format the SD card when updating, rom dropping to monitor in c65 basic is known and also SD card related. Try other cluster sizes please!
If someone wants to take care of our SD compatibility problems, let us know. For now they are not top pio. Cheap 1GB and 2GB cards and standard windows format option will always do the trick. But yes, we need more people covering side-tasks and enhancing/finishing them!