while you answer chibaguy's questions (needed), I would make sure that all the needed files are on the server. If you uploaded them by means of ftp, use some ftp program to compare the file tree of whatever version of Tiki your are using (upgrade to 3.7 or 5.2 if needed), and click on synchronize the files to upload whatever missing files you need to upload still or re-upload.
Ensure also that your server/host meet the Requirements to use Tiki. (it should, but you'd better double check, to avoid headaches and possible confusion in this field)
Hope this helps.