HELP! Disk locked on Kobo Glo

Hi, just bought a Kobo Glo after having used the Touch for some time. However, after putting a bunch of books on the device, its flash drive now appears to be locked. There's no way I can put anything on or delete any books; even a factory reset won't work. Does anyone have any suggestions (is there a way to access the factory reset through the hardware?)? I'd be grateful for some hints.

Apple Disk Utility gives this analysis (but can't repair anything):

Verifying volume “KOBOeReader”
Checking file system** /dev/disk1
** Phase 1 - Preparing FAT
** Phase 2 - Checking Directories
/.kobo/KoboReader.sqlite-journal starts with cross-linked cluster (125834)
Truncate? no
/.kobo/KoboReader.sqlite-journal: Cluster chain starting at 125834 is cross-linked at cluster 125834
Truncate? no
size of /.kobo/KoboReader.sqlite-journal is 4640, should at most be 0
Truncate? no
/.kobo/Kobo/Analytics.conf starts with free cluster
Truncate? no
/.kobo/Kobo/Analytics.conf: Cluster chain starting at 125668 ends with cluster marked free
Truncate? no
size of /.kobo/Kobo/Analytics.conf is 173885, should at most be 4096
Truncate? no
** Phase 3 - Checking for Orphan Clusters
Found orphan cluster(s)
Fix? no
Found 47 orphaned clusters
Free space in FSInfo block (259239) not correct (259238)
Fix? no
2584 files, 1036952 KiB free (259238 clusters)