The December Microsoft patches held a special surprise for Windows XP SP2 users of Internet Explorer 6.
One of the Critical fixes was KB942615. It appears that this was packaged without the registry addition added in KB942367. Here's a thread from Microsoft's Internet Explorer newsgroup describing it. Here's a Microsoft engineer's comments.
Without this, IE6 crashes sporadically, especially when opening gmail. One comment suggested that it was triggered by pages which validate their login with https:// before the page proceeds to load normally with http://.
Here's a link to a zip file that contains the registry hack from KB942367.
You don't even have to restart your PC. Just close all the copies of IE6 before you apply the registry hack.