Not sure if your still watching, but recently had the same issue with this sil3512 dropping a disk. What i did was removed the drive from the raid1 array.
Then downloaded this program and checked the disk:http://www.cgsecurity.org/wiki/TestDisk_Download
Disk had an issue with partition table, it fixed the problem.
Then i dragged the disk in the raid software management system (left hand paine) back into the window where your SYNC drive is. It started to rebuild the array again. Been waiting 10 hours now 16% done. '
I have two 2gb WD drives.
Live fast and prosper!