Same kind of problems have been reported in the french community site (see http://www.ezpublish-france.org/index.php/fr/forums/questions_techniques/connexion_impossible_a_ez)
Nothing to do with disk space, nor IE (happen with Opera, IE and Firefox on both Linux and Windows client)
Have really no idea why, seems to me to be random except that:
- I didn't notice it before upgrading to 3.6.x - Seems to happen on website run on an IP address
Would like to make it as a bug but I need more info...
Through a mistake in an .htaccess file, I created a situation where no form could be submitted. As a test, you might want to try to submit a contact form on your site. If it works, you should see a confirmation page showing you results of your submission.
If it does not, you will get a blank page. If you get a blank page, the culprit is very likely the rewrite rules in either the .htaccess or httpd.conf.