I'm not sure what caused it but it just keeps looping the rebuild process. Gets to 100% of re-syncing and then starts at 0% again...
Just interested in a solution but not finding anything with D-Link. The only reference to reproduced problem... More details available: http://forums.dlink.com/index.php?topic=50417.0
I decided to pull the drive and wipe it clean in another PC. Removed all partitions on that machine, put it back in the NAS. Now it won't let me check the "Reconfigure to RAID1" box... :-/