Windows Azure: Can't upload a 34 MB file on to the blob

Blobs larger than 64MB must be uploaded using block blobs. You break the file into blocks, upload all the blocks (associating each block with a unique string identifier), and at the very end you post the list of block IDs to the blob to commit the entire batch in one go.

Uploading in blocks is also recommended for large blobs less than 64MB in size. It is very easy for a hiccup in the network connection or routing through the internet to lose a frame or two in a very large upload, which will corrupt or invalidate the entire upload. Use smaller blocks to reduce your exposure to cosmic events.

More info in this discussion thread: http://social.msdn.microsoft.com/Forums/en-NZ/windowsazure/thread/f4575746-a695-40ff-9e49-ffe4c99b28c7