http://bugs.winehq.org/show_bug.cgi?id=17035
--- Comment #5 from Simon Paridon Simon.Paridon@uglyhorst.de 2011-01-30 05:34:43 CST --- Some correction: in the original post, I said something about switching to a different task, this is inaccurate. Instead, it happens if you focus another Wine window, and then refocus the Script Editor.
It does NOT occur if you switch to a non-Wine app and back. It DOES occur if you switch to another RPG Maker window, like the search dialog. So, switching the task was inaccurate. Sorry.
Also, about the effect, it does not only select the entire text, but it also repositions the cursor to the beginning of the text and therefore scrolls all the way up. It's really annoying because every time it happens, you'll have to scroll down again to find where you were.
No idea if this is relevant at all (probably not), but disallowing the window manager to decorate / take control of the Wine windows doesn't change anything.
This was tested in 1.3.12.