On Windows 7 with IE8, make sure the edit page is scrolled all the way to the top and click a WikiEditor button (such as Bold) or use a dropdown (such as Heading). The entire browser page scrolls downward and the button/dropdown does not insert any text into the edit box.
Now, leave the browser window in its current (scrolled) state and click the button (or use the dropdown) again. The proper text gets inserted.
Scroll the page back up to the top. Click the Bold button again. Same behavior: the browser scrolls and nothing gets inserted.
This bug feels similar to 31847 and might be related. It happens only on Windows 7 (as far as I can tell). It happens on Wikipedia right now (1.18wfm1 r101368), and also on Mediawiki 1.17.0 that has been patched with the solution to the related bug 31847 (i.e., r100398).
The bad behavior happens regardless of whether the cursor focus is in the edit box, or whether text is highlighted in the edit box. I also turned off all additional features in Preferences (Side-by-side preview, etc.)
I tried this on a non-Windows-7 system (Windows 2008 Server) with IE8 and could not reproduce the problem. But it was easy to reproduce on Windows 7.
Version: unspecified
Severity: normal
OS: Windows 7
Platform: PC
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=31847