Assuming you're talking about new blobs, please check this issue: http://code.google.com/p/googleappengine/issues/detail?id=4872.
I think there is no "good" workaround yet. -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-appengine-java/-/nHGG3gfSqwgJ. To post to this group, send email to google-appengine-java@googlegroups.com. To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.