dump trying to access incorrect block numbers?

[Michael Butler]

Recent builds doing a backup (dump) cause nonsensical errors in syslog:

Jul  7 00:10:24 toshi kernel: 
g_vfs_done():ada0s3a[READ(offset=6050375794688, length=32768)]error = 5
Jul  7 00:10:24 toshi kernel: 
g_vfs_done():ada0s3a[READ(offset=546222112768, length=32768)]error = 5
Jul  7 00:10:24 toshi kernel: 
g_vfs_done():ada0s3a[READ(offset=2142846844928, length=32768)]error = 5
Jul  7 00:10:24 toshi last message repeated 7 times
Jul  7 00:10:24 toshi kernel: 
g_vfs_done():ada0s3a[READ(offset=2226879725568, length=32768)]error = 5
Jul  7 00:10:24 toshi kernel: 
g_vfs_done():ada0s3a[READ(offset=2941159211008, length=32768)]error = 5
Jul  7 00:10:24 toshi last message repeated 2 times
Jul  7 00:10:24 toshi kernel: 
g_vfs_done():ada0s3a[READ(offset=3067208531968, length=32768)]error = 5
Jul  7 00:10:24 toshi kernel: 
g_vfs_done():ada0s3a[READ(offset=3277290733568, length=32768)]error = 5
Jul  7 00:10:24 toshi kernel: 
g_vfs_done():ada0s3a[READ(offset=3487372935168, length=32768)]error = 5
Jul  7 00:10:24 toshi kernel: 
g_vfs_done():ada0s3a[READ(offset=3697455136768, length=32768)]error = 5
Jul  7 00:10:24 toshi kernel: 
g_vfs_done():ada0s3a[READ(offset=3865520898048, length=32768)]error = 5

FSCK declares nothing to be wrong with the file-system. I even used the 
'-r' inode reclaim option and '-Z' to zero unused blocks to no effect.

I now have two UFS-based systems showing the same symptoms - what's up 
with this?

	Michael