Is It Possible For A Supreme Court Justice To Be Too Conservative?

With justice Stephens retiring there is a lot of talk about who will replace him and whether or not they'll be too liberal (high probability), but with this discussion came talk of the Democrats in the Senate objecting to nominees who were too conservative.  I had to ask myself if it's even possible to be too conservative in that position.

What is considered conservative in the Supreme Court?  That would be a strict adherence to the writings and intent of the Constitution and all it's amendments.  If that's the definition then how can they be too conservative?  If they read the Constitution so strictly that they interpret it to mean something it doesn't, then they're no longer conservative but liberal again. 

What I don't understand, and probably never will, is how appointing somebody who believes in the original intent of the Constitution to a job whose sole role is to interpret the original intent of the Constitution and determine whether a law falls within those guidelines or not can be a bad thing.  How is there any justification for a stance of hiring somebody for that job who DOESN'T hold to the original intent of the Constitution?  What's the point of having a Constitution if we can stray from it as long as the court says it's ok?

I admit that I'm a Constitutionalist and I believe the country would be in much better shape if the entire Supreme Court was now and always had been made up of justices that bordered on being too conservative.