IE7-Display problem

As you can see i [1] the Tabs works correctly. But then on the third tab the content auf tab3,4,5 are displayed together. In addition you cannout swith back to Tab1 or 2.
[1]http://picfront.org/d/s8N6rTxf7N/screenshot1.jpg
[2]http://picfront.org/d/fYOCEa1gB/screenshot2.jpg
My theme-Code:
$form['tabblock1'] = array(
'#type' => 'tabset',
);
$form['tabblock1']['tab1'] = array(
'#type' => 'tabpage',
'#title' => t('Allgemein'),
'#content' => $nallgemein,
);
$form['tabblock1']['tab2'] = array(
'#type' => 'tabpage',
'#title' => t('Kontakt'),
'#content' => $nkontakt,
);
$form['tabblock1']['tab3'] = array(
'#type' => 'tabpage',
'#title' => t('Lieblings...'),
'#content' => $nliebl,
);
$form['tabblock1']['tab4'] = array(
'#type' => 'tabpage',
'#title' => t('Beruf/Ausbildung'),
'#content' => $nBeruf,
);
$form['tabblock1']['tab5'] = array(
'#type' => 'tabpage',
'#title' => $node->name.'`s '.t('Blog'),
'#content' => $blogs,
);
I hope you can help me.