While doing a full optimize, UltraDefrag consistently crashes ("UltraDefrag GUI Interface has stopped working."). I haven't gone further than about 5% yet, usually 1% or 2% when it crashes.
I have the same issue, but it does it with defrag, quick, and full. Running windows 7 Ultimate 64bit on AMD.
Can only add a little to the OP and previous comment. Finished the patch-to-the-patch-to-Patch-Tuesday routine before upgrading, so Win7 was up to date. Installed 7.0.0 beta2 for 64-bit on top of 6.0.2. Cold restarted and ran full optimization. Got about 5% done when it crashed ("Ultra Defrag has stopped working"). The portion of the drive that had been moved, but not put back was showing gray at the bottom of the screen. Uninstalled, cold rebooted, installed 6.0.4. The previously moved stuff was still showing gray at the bottom of the screen, but full optimization did its normal thing otherwise. Ran Windows disk check afterward (GUI, not command line) with the switch to fix file system errors, but not to recover bad sectors. Restarted. Fired up 6.0.4 again, analyzed and the previously gray portion of the drive is now looking like normal. I have no clue as to why 7.0.0 crashed. The F8 report function produced nothing.