Don't put
WarpSharp.dll in your plugins directory. It is well-known to break autoloading, resulting in just the kind of crash you describe.
Instead, put it in some other directory and load it manually at the top of your SSXSharpen script.
If you're using the same version of FastLineDarken I am, then the only DLL you should need for that is
MaskTools 1.5, which is available here:
http://avisynth.org/warpenterprises/