Was getting this:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>  
<error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata">  
  <message xml:lang="en-US">One of the request inputs is not valid.</message>

When calling UpdateObject from the Azure SDK when using the table storage emulator. Turns out the emulator doesn’t exactly emulate as per MSDN documentation: http://msdn.microsoft.com/en-us/library/gg433135.aspx “The storage emulator does not support Insert-Or-Replace Entity or Insert-Or-Merge Entity, known as upsert features.”

So, to work around, I changed the code to delete then reinsert.  Or not. Turned out I had lots of concurrancy problems with doing a delete/insert which were resolved with the more transactional upsert.