Does cmd-line ftp call explore.exe?

[mary r]

I'm being told by a tech rep for a customer's web-hosting company that my ftp
script is opening explorer.exe and locking the file I'm trying to "put" a
replacement of.

My batch file is:
J:
cd \MyDirectory
ftp -s:myscript.txt myftpsite.com

My script file is:
MyFtpId
MyFtpPwd
hash
put "MyFile.pdf"
quit

I actually tested this with the addition of the "-d" param before the "-s"
param:
ftp -d -s:myscript.txt myftpsite.com

just to see all the prompts and actions. Nowhere was explore.exe explicitly
invoked.

The problem is that MyFile.pdf is being held in an "open" state by
explore.exe and thus cannot be replaced, renamed, or deleted. Tech support
has told me that my script is the origin of the open Windows Explorer
processes.

Being a scripting novice, I can't find any indication of how/where it is
being initiated in my simple little script that's almost an exact copy of the
sample script from the KB.

Please help!
TIA-
-mary r