With the latest version, you are only able to select the last 2 digits of the time. If you are using HH:MM then its the minutes part. If you are using HH:MM:AM/PM then it's the AM/PM part.
To move to the other parts of the time you have to use shift+tab as using the mouse to select that part of the input doesn't work.
This behaviour can be seen on the main Time Entry page keith-wood.name/timeEntry.html when using IE8.
1.5.2 is the last version that seems to work fine in IE8.