Tabbing issue

I created a form using as3 and set the tabIndex for all the fields liek this:

ActionScript Code:
[LEFT]</p>
<p>cusname.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]1[/COLOR];</p>
<p>cuscompany.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]2[/COLOR];</p>
<p>cusaddress.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]3[/COLOR];</p>
<p>cuscity.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]4[/COLOR];</p>
<p>cusstate.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]5[/COLOR];</p>
<p>cuszipcode.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]6[/COLOR];</p>
<p>cusphone.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]7[/COLOR];</p>
<p>cusfax.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]8[/COLOR];</p>
<p>cusemail.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]9[/COLOR];</p>
<p>cuspreferred.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]10[/COLOR];</p>
<p>projectname.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]11[/COLOR];</p>
<p>projectduedate.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]12[/COLOR];</p>
<p>projectspecs.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]13[/COLOR];</p>
<p>selectpic.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]14[/COLOR];</p>
<p>upnews.[COLOR=#0000ff]tabIndex[/COLOR] = [COLOR=#000080]15[/COLOR];</p>
[/LEFT]

It tabs fine until it comes to the cusstate which is a ComboBox. If i manually move it to cuszipcode it works fine again until it comes to cuspreferred which is also a ComboBox. Moving it ahead it tabs as normal until it reches selectpic which is a Button.

Is there something special I need to do for these types of fields?