Hi,
I created a WCF Service Application project and then added nuget packages to enable me to use entity framework and Windows Azure. After this point. all my services were getting the following error:
Error 5 'DataServiceProtocolVersion' is ambiguous in the namespace 'System.Data.Services.Common'.
Which was referencing this line of code:
config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V3
In-particular the DataServiceProtocolVersion enum
After doing a lot of searching around on the web. I could not find any solution to this, so I started to go through removing references. (Thinking that something I added with Nuget is causing the conflict)
I removed the System.Data.Services.Client reference and Everything started working again.
I then used the Object Explorer which showed that DataServiceProtocolVersion now resided in the:
Microsoft.Data.Services.Client
Assembly.
Just posting this in case I can help save some time for anyone else who is suffering from this issue.
VB Magic 
I had this problem. You saved me. Thanks.
Comment by Jose Cifre — 2013/04/08 @ 11:01 pm
thanks for helping to narrow it down for me! Not sure if they have changed or not, but this worked for me:
config.DataServiceBehavior.MaxProtocolVersion = Microsoft.Data.OData.ODataVersion.V3
Comment by Terence F — 2013/07/21 @ 7:34 pm
You saved a lot of my time, I was getting this error, had removed re-added the packages but the error will still apear, deleting the reference solved my problem.
Thank you very much for sharing.
Comment by Zubair Ahmed Khan (@Zubair530Ahmed) — 2017/02/10 @ 4:12 am