Hi Bob,
2.2.7.9 was the last version of mojoPortal to target 2.0 .NET, it now targets .NET 3.5 sp1. If you install .NET 3.5 sp1 it should resolve the error.
Its still possible to create a 2.0 compatible build but you would have to do it yourself with VS 2008 by changing the target back to 2.0 and removing any files it complains about when you try to build the solution.
Hope it helps,
Joe