For all of you  building Windows Azure solutions based on SDK 1.5, please see this blog post and update your projects accordingly:

The fixed version of the SDK is 1.5.20928.1904, so please check your installs and update as soon as you can if you are on a lower version. Impacted functions are DownloadToStream, DownloadToFile, DownloadText, and DownloadByteArray methods for Windows Azure Blobs. Details in above link.