Defect using mouse scroll wheel under Vista

Under Microsoft Vista, when you attempt to use the scroll wheel to scroll your document it does not work even if the document has focus - the focus is shifted to another area of the form. ie. Treview, textbox etc. The issue does not appear when using Windows XP.

I can replicate the issue not only in my own program, but using your sample. Also there is no issue scrolling other windows or controls such as Internet Explorer, Microsoft Word/Excel - just the syntax editor document.