After installing KB3114409, Outlook 2010 started only in safe mode, even when told not to do so. Removing KB3114409 solved the problem.
wusa /uninstall /norestart /kb:3114409
QA at Microsoft keeps lagging behind. A few weeks ago, HTML email made Outlook 2013 crash due to “improved” font handling, courtesy of KB3097877. Others were unlucky and couldn’t login until KB3097877 was removed. Curiously, RDP remote login wasn’t affected.