I would check the files like I said for starters. And see if it is just a couple of files that have a problem. It may be just some need to be corrected for either permissions or replaced.
Since you don't have ftp right now.
As far as moving to mindraven I think you will be extremely pleased with the service. I know I am.
As far as the cache folder.
normally you can delete all the files except for the html file.
They get rebuilt on their own.
