Forum OpenACS Q&A: upload file problem

I am having trouble with uploading files (the form var for the uploaded file is upload_file):

Error: could not read "": no such file or directory
could not read "": no such file or directory
    while executing
"file size $tmp_filename"
    invoked from within
"if { ![info exists upload_file] || [empty_string_p $upload_file] } {
    append exception_text "<li>Please specify a file to
upload
"
    incr except..."

Here's the actual code snippet...

if { ![info exists upload_file] || [empty_string_p $upload_file] } {
    append exception_text "<li>Please specify a file to
upload
"
    incr exception_count
} else {
    # this stuff only makes sense to do if we know the file exists
    # ns_queryget:
    #   http://www.aolserver.com/docs/tcldev/tapi-c98.htm#191488	
    set tmp_filename [ns_queryget upload_file.tmpfile]

    set file_extension [string tolower [file extension $upload_file]]

    # remove the first . from the file extension
    regsub "." $file_extension "" file_extension

    set guessed_file_type [ns_guesstype $upload_file]

    set n_bytes [file size $tmp_filename]

The ns_queryget doc says...

set x [ns_queryget name]

If "name" is a key in the query data, the variable x will be set to the value associated with the "name" key. If "name" is not a key in the query data, "" will be returned. It appears that

set tmp_filename [ns_queryget upload_file.tmpfile]

is setting tmp_filename to "" suggesting that upload_file.tmpfile "is not a key in the query data."

I lifted most of the code from /pvt/portrait/upload-2.tcl. What am I missing? -- Thanks.

Yes -- I am using POST:

form enctype=multipart/form-data method=post

Andrei - Thanks for your reply, but no, I am not running WinNT -- I am running Red Hat 6.2.