I am getting this error from the Disk Optimizer, after upgrading to W 8.1 Pro from W 8.0, on TWO different partitions on a 2 TB HDD that has THREE partitions. The third one, I just reimaged it for a W 8.1 Pro Lab, which OPTIMIZED OKAY. My System 1 TB HDD drive with 3 partitions optimized fine. At the present time, the only Flash Drives I have are Thumb Drives (Jump Drives) which are NOT "check off" for optimization.
I DO NOT have any SSD's!!!
Thank You for your attention to this issue,