I’ve created a combo box in a form using the following:
<select id="end_minute" name="end_minute">
<option value="00">00</option>
<option value="15">15</option>
<option value="30">30</option>
<option selected="selected" value="45">45</option>
</select>
In Firefox, he first option is selected, but in IE the option with attribute selected="selected" is (correctly) shown.
Update
Pekka is right, the values were being cached by Firefox
You are probably re-loading the page after having selected the first option. Firefox will memorize form values in that case. When you go to the address field and hit Enter, it should return to normal.