齐鲁证券通达信安卓版:为何更改文件名之后aspupload组件就出现访问被拒绝现象？

这段代码
<%
thumbspath="movie_update/image/0040thumbs-闪电奇迹.jpg"
uploaddir=server.mappath("/")
response.write uploaddir
sizelimit=409600
if request.querystring("upload") = "yes" then
set uploadfile=server.createobject("persits.upload")'创建aspupload对象
uploadfile.setmaxsize sizelimit,true'限制上传的文件大小(字节)
uploadfile.createdirectory uploaddir,true'如果目标文件夹已经存在，则忽略错误
uploadfile.save()'先将文件保存到服务器内存
if err.number=8 then
response.write("文件体积不能超过"&sizelimit&"字节")
elseif err.number <> 0 then
response.write("发生了错误，我们对表示抱歉")
end if
set file=uploadfile.files("thumbsfile")
if not file is nothing then
filename=file.filename'filename为上传文件名
fileext=file.ext'fileext为上传文件扩展名
file.saveas uploaddir&"\"&replace(thumbspath,"/","\")
response.write("文件已上传")
end if
end if
%>
运行会出现访问被拒绝错误
但是如果把file.saveas 后面改为file.saveas "z:\website\bac.jpg"
却可以正常上传，这是何故？