MVC4 , error never seen before

This was when I was using Chrome. When I run the app in IE it is prompting me to download my controller? Doesn't make any sense....

Here is my code for my get method.

The problem is try to populate a drop down list. I get the error as soon as I try to populate the viewBag.libraryId

ViewBag.libraryId = ReturnLibraryFolderSelectList(libraryFolderRepository.ReturnList(ClientId), package.libraryFolderId);

Here is my Base Controler that the ReturnLibraryFolderSelectList is from:

  public SelectList ReturnLibraryFolderSelectList(IList<LibraryFolder> libraryfolder, int libraryFolderId)
        {
            LibraryFolder gbl = new LibraryFolder() { description = "Select a Folder", id = NEW_INT, inactive = false };
            libraryfolder.Insert(0, gbl);
            return new SelectList(libraryfolder, "id", "description", libraryFolderId);

        }

  public class LibraryFolder : BaseModel, ILibraryFolderRepository
    {

        public int id { get; set; }

        //the value of the description for the dropDown

        [Display(Name = "description")]
        [Required(ErrorMessage = "description is required")]
        public string description { get; set; }
       
        [Display(Name = "Client")]
        [ForeignKey("client")]
        public int clientId { get; set; }
        public virtual Client client { get; set; }

        /// <summary>
        /// whether the language is inactive
        /// </summary>
        [Display(Name = "Inactive")]
        [Required(ErrorMessage = "Inactive is required")]
        public bool inactive { get; set; }


        public IList<LibraryFolder> ReturnList(int clientId)
        {
            return db.LibraryFolders.Where(l => l.clientId == clientId && l.inactive == false).ToList();
        }