After update to WP 3.4 i got an css error (no layout) in IE 8 on xp machines. on IE 9 on a windows vista machine the problem existed also. IE 10 on windows 7 works fine. After de-activation of the seo plugin, IE 8-9 on the xp and vista system worked well again.
Later i found out that i also update the ceo plugin to version 1.2.3
After downgrade to 1.1.9 everything worked fine again. All versions from 1.2 have the same problem.