Bitwise shift

I'm bitwise shifting integers(optimized algorithms).
The problem is when they switch unsigned/signed representation and the results are wrong.Can anyone explain how to fix this?

Op: What CFlags are you using? Have you tried compiling your code on any type of a SPARC processor to be sure? I ask this because SPARCS use different indian bits, so you might not run into these problems. Or you might get different ones, I'm not sure. As an undergraduate Computer Science Student, I don't get to interact with SPARC processors. In fact, all I get to use is Scheme. I'm posting this from my Schemeing rig as a matter of fact.