Compiler having trouble with referencing an assembly

I've created a Class Library project called Core. The default namespace is XXX.Tasker.Core.

I've created another Console project which references Core. In my Main() I've got some calls to stuff inside the Core but I'm getting an error:

The type or namespace name 'Core' does not exist in the namespace 'XXXX.Tasker' (are you missing an assembly reference?)

The only thing I can think of is that the fact my assembly name i开发者_StackOverflow社区s Core might be confusing it.. but that really doesn't make much sense.

Any other suggestions?

The problem turned out to be that Core was compiled as .Net Framework 4 and the Console was .Net Framework 4 Client Profile. Apparently you'll just get really weird errors instead of a proper notification when this occurs.. thanks MS! ;)