I am also having this problem with my sharepoint site. I have not changed any configuration options. I have an E3 plan.
I can confirm this that my users in Canada are not having this problem but my users in India are facing this exact issue.
This has been happening to me since last night. I have a ticket open with support but we are still trouble shooting the problem.
It looks like many people are having the same issue.
http://community.office365.com/en-us/forums/154/t/82739.aspx
http://community.office365.com/en-us/forums/154/t/83100.aspx
Any help would be welcome.
Thanks