I have the same problem. Yesterday, all modules had their content. Of course that was after a whole day where a module with a grid in it was showing "Error". At the end of the day, without any action on my part, the grid content showed up.
Today, upon first login, all modules are blank and only the home page module, that you can see without logging in, has its content.
Upon building today (no change in design or code anywhere in the project), I got 10 errors from classic.ascx. I have not touched that and don't know what it is or what it does, except for a google search.
Is there any resolution on this yet?
MichaelM