I'm using a wordpress multisite, installed in August 2012 on shared hosting by 1and1.com, not my choice, btw.
After updating wordpress yesterday, the media section is no longer resizing thumbnails. Upload isn't a problem, but the thumbnails aren't produced any longer as they were until yesterday's update.
Due to the istallation date, as far as I understood, the upload path is /blog.dir/. When installing a new blog and setting the upload path on network -> site settings to /blog.dir/NEWBLOGNUMBER/files, the thumbnails are produced for today's new blog, but not for the existing blogs with the same path setting.
Any ideas how to solve the problem?