I love Google (and I really do like every web product they produce), this is just inexcusable.
Google has apparently lost the personalized homepage preferences of hundreds of users, and over 150 people have posted as having the problem on Google Groups since 6:45 am. Users are coming into their accounts and seeing them rolled back several months, losing the last few months of customizations, and any attempt to edit their pages and fix it gets rolled backwards.
So Please Do not change your homepage theme until the problem has been solved.
That’s what Google has to worry about with stuff like this. No matter how good your software is, if it crashes, loses data, is unavailable, or just has weird bugs, people will desert you and all your hard work will be for nothing.