You seem to be getting this problem due to internal clash between two different extensions of the index file in that perticular folder. Try naming the second one something else and trying out.
If it doesnt work even then, then try to re-upload all your data in binary format onto the server.
In your ftp upload methods, you will have three mods.............binary, ASCII and automatic.
By default the automatic method is chosen, so change it to the binary mode and then reupload all your data.
