If you should happen to create a new cloud services project in VS2008 with VB settings, you may well find that you are unable to save the project/solution. The message is, in typical fashion, singularly useless:
Luke H's blog pointed me in the right direction. The solution is to enable saving projects on creation. Under Tools >> Options, select Projects and Solutions.
Make sure "Save new projects when created" is checked. Restart Visual Studio, and you'll be good to go.