Open a XAML file. Press Ctrl+H to replace some text. The new inplace-search box is displayed. Now press <TAB> to type the replacement text. Instead of moving the focus, Visual Assist "auto-completes" the selected word in the active document.
You have to fix this! VAX makes XAML editing impossible.
I am able to repro. case=79124. Sorry for the trouble. Until fixed, you can add .xaml to the Extension to ignore list on the File Handling page of the VA Options dialog.