Removing MyDefrag with its uninstall utility doesn't fix the problem. (BTW, does that completly remove all traces of MyDefrag? If not, how do I accomplish that?)
Yes, the MyDefrag uninstaller will remove all traces.
Does MyDefrag have something to do with my Disk Defragmenter problem?
MyDefrag is a clean program, it does not affect any other program in any way. However, different defraggers have different ideas about how to optimize a disk. For example, MyDefrag uses an advanced concept called Wrap-Around Fragmentation, unknown to other defraggers. It is therefore entirely possible that another defragger will think a disk needs to be defragmented, even though the disk is perfectly optimized by MyDefrag. For more information see the first bullit in Why does MyDefrag not perfectly optimize my disk?
how do I fix it?
Uninstall the other defragger. MyDefrag is the best.