I haven't read all of this topic, but one of the most common problems with defrag tools is having insufficient free space on your hard disk for them to work.
If you have less than 15% free space on your hard disk you are looking at having problems with most defrag tools. You could try the windows defrag, whilst not as fast as puran, it may require less resources, but even windows defrag if you get below 15% free space I think it warns you.