This bug looks like related to the video card or associated video driver, but it only happens when I press the "Defrag" button.
How to reproduce this bug:
1- I move one by one 4.3 Gb. files to another drive.
Every time I move one file I press "Analyze" and then "Defrag"
2- Once the file has been defragged, I transfer the next file and repeat the step 1.
Defraggler is always open, I do not close it.
After repeat this proceeding for around ten times the blank screen shows up.
If I move the mouse, I can see the objects reappearing again, such us the buttons, the Windows taskbar and so on.
The way to correct this is restarting Deflagger.
This bug could be correlated to the post "Defragler uses excessive GDI objects" ---> http://forum.piriform.com/index.php?showtopic=23284
I am running Windows XP SP3 with a Nvidia 7800 GS card