SQL Connection dropping

[C# Programming]

I have a series of strongly typed datasets in my .NET v2 project. When I shift the project to .NET v3.5 the system runs the first connection but refuses any further connections giving me a Named Pipes error...

I thought that there were no code changes required to migrate from v2 to v3.5, well obviously there should have been because it no longer works, but what should I be looking for?

Any ideas?

Thanks