Error asp when I reduce minuscule url

[jackal Profile]

Hi to everybody, I have installed from over two years the form rewrite Version 3.1.0.82.
Some days ago I have brought a change to the file.htaccess to change the url from capital to minuscule.

RewriteMap lc int:tolower
RewriteCond %{REQUEST_URI} [A-Z]
RewriteRule (.*) ${lc:$1} [R=301,L]


I have realized however that when in my server I go to use a file asp classic to give the upload of a file pdf
I receive this error.

Error of run-time of Microsoft VBScript error '800a0005'

Call of routine or I deduce not valid: 'MidB'

If I eliminate the line in the file.htaccess instead everything works.
Do you have some suggestion to give me?
Thanks