IE woes; alerts can not be dismissed in IE8 (HTML5 DocType, non-compatibility mode). Although the delete icon (the t-dismiss DIV) is rendered in the correct place on the screen, it does not respond to mouse clicks and the mouse pointer does not change to "pointer".
It seems the problem occurs because the dismiss is floated. Removing the float in favour of right positioning enables the dismiss to be clicked again.
The following CSS changes solve the issue.
/* The dismiss button on IE can't be clicked if it's floated!??? */
/* compensate for non-floating */