I suggest try uploading the files again. Then if the problem continues I would try recycle the application pool. Then if that fails to solve it I would ask the host to either move your site to another server or re-install/repair the .net framework.
If you google the error:
"Exception type: HttpCompileException Exception message: External component has thrown an exception. at System.Web.Compilation.AssemblyBuilder.Compile()"
you will find advice like what I have suggested