Some people have asked so:
1) When I do tests or maps or answer questions I never do them on a a theme.msstyles. I always have some test.msstyles I work with. These are just copies of aero.msstyles I copy and paste to my desktop and rename. I open these in WSB do my changes and keep testing them until I'm satisfied. If I want them in my theme.msstyles then I open that and make those changes.
2) If you make changes to your theme.msstyles and screw up then before doing anything always have copies of your theme, msstyles and anything else so you can use these to replace something bad that you've done. Before changing an image export the original to your desktop so if you screw up the change you can always import the original back in. Always have backups of everything. I have actually accidentally replaced my theme.msstyles with aero and had to recover using a backup of my theme.msstyles! Back up all System File changes too.
3) If you forget to do all of this you can always go back to aero.msstyles, open it with WSB, export a clean copy of an image you messed up, open your theme.msstyles and import the clean image to replace the bad one. Of course if you had made changes to that image beforehand you'll have to make them over again. I don't know how many times I've had to go back to aero.msstyles for image recovery!
4) Here's a recovery method from way back. Never used it but should work:
http://vistastylebuilder.com/forum/index.php?topic=163.05) When you compile and save a shellstyle all resource editors will make a copy of the original like shellstyleoriginal.dll. If you screw up your shellstyle and you can get back to the shellstyle just delete your new one, rename the original shellstyle.dll and reboot.
6) If you have screwed a shellstyle so bad you can't even get back to change it then do a system restore. If you can't even get to system restore then go to Windows Recovery in bios before you boot into Windows ( in my case I have to press F8. Find out what it is for your computer now so you will be prepared) and do a system restore from there. This goes for System Files disasters too.
7) When WSB won't let you save or test just go back and try again.
8) If you get screwed so bad you end up in Windows Classic remember WSB won't work there. Go into Personalize and apply an aero theme. Then open up your theme in WSB, save and apply it. Sometimes you have to save and apply twice to get it to work.
I think I have experienced every screw-up and error possible. If there are other ones I can help with let me know. If there are other methods of recovery feel free to add them here. Thanks.