[DiapDealer]

Forget all the creating/styling in Code View and then flipping to Book View to undo said styling. I'm not near my development machine, but here's what I'm getting:

1) Open Sigil and go directly to Book View
2) type some words
3) highlight any portion (just not the whole thing) of what you type and style it (bold, italic, strike, sub- super-script--whatever you want), then immediately unstyle it (click the same style button)
4) switch to Code View
Crash

The short of it is: styling and then immediately unstyling anything other than the entire contents of what is in Book View will result in a crash when switching to Code View.

The only exception is that you can unstyle a portion of what you originally styled and the crash doesn't happen when switching.

Select the entire contents of Book View and style/unstyle: you'll get no crash when switching.

Select a portion of the contents of Book View and style/unstyle the same portion: it crashes when switching.

Select a portion of the contents of Book View and style it and then unstyle only a portion of what you styled: no crash when switching.

It suggests some flaky QCursor behavior on Windows to me. I'll try to get some debugging output this weekend some time.