1. Make sure the "Labels" box is checked: Page Elements> Blog Posts> Edit (Mine was no longer checked... odd) Note you may have changed the "Labels" box to something else, like "Tags".
2. Go to Design > Edit HTML and Download Full Template (this is your backup just in case)
3. Click on the check box which says “Expand Widget Templates”
4. Look for <b:include data='post' name='postQuickEdit'/>
<b:loop values='data:post.labels' var='label'>
<a expr:href='data:label.url' rel='tag'><data:label.name/></a>
<b:if cond='data:label.isLast != "true"'>,</b:if>
5. You can click "PREVIEW" and view your work before committing with "SAVE NOW".
As you can see on my posts, I now have my labels back.
Source for most of this: http://www.google.com/support/forum/p/blogger/thread?tid=2ebc44aed318124b&hl=en
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