JavaScript problems since upgrade: Edit Post page

I upgraded from 3.4.2 to 3.5 and am having JavaScript problems. I was able to alleviate some by disabled one old plugin (Ad Sense Manager), but problems on the widgets page and the edit post page continues. When I click on a post to edit, there’s nothing in the tags box even though tags show on the post list-view page. When I view source, I see two separate tags form fields – the first one is not displaying:

<div id="post_tag" class="tagsdiv">
<div class="jaxtag">
<div class="nojs-tags hide-if-js">
<p>Add or remove tags</p>
<textarea id="tax-input-post_tag" class="the-tags" cols="20" rows="3" name="tax_input[post_tag]">list of tags on the post here</textarea>
</div>
<div class="ajaxtag hide-if-no-js">
<label class="screen-reader-text" for="new-tag-post_tag">Tags</label>
<div class="taghint">Add New Tag</div>
<p>
<input id="new-tag-post_tag" class="newtag form-input-tip" type="text" value="" autocomplete="off" size="16" name="newtag[post_tag]">
<input class="button tagadd" type="button" value="Add">
</p>
</div>
<p class="howto">Separate tags with commas</p>
</div>
<div class="tagchecklist"></div>
</div>

So, it seems that js isn’t working, but it’s showing the fields built to require js.

I read through this thread, but do not have the plug-ins or mods mentioned. I’ve reverted to the default them and disabled all plug-ins, but the problem still persists.