debug captcha explore show error!

because my ie dont show the encurtity code,so i debug the CAPTCHA_image.asp,then ie show me the follow error,why?
i need your help!thx

B
Vbscript Runtime error 'ASP 0185 : 13'

Type mismatch

/forum/CAPTCHA/CAPTCHA_image.asp,line 865

Private Sub writeBinary(strHex)

    Dim lngHexLoop
    Dim strwrite
    
    'Remove any spaces (Error handling (there should not be any spaces anyway))
    strHex = Replace(strHex, " ", "")

    'Loop through the in steps of 2 for each 2 character hex
    For lngHexLoop = 1 to Len(strHex) step 2
        'Write the binary output
 865       strwrite=ChrB(CByte("&H" & Mid(strHex, lngHexLoop, 2)))
        Response.BinaryWrite strwrite
    Next
End Sub

in fact when i down  the   CAPTCHA source ,then i put it in my apache_root directory,then i explore the  /CAPTCHA/CAPTCHA_image.asp, then the explore show me the error message,
B
Vbscript Runtime error 'ASP 0185 : 13'

Type mismatch

/forum/CAPTCHA/CAPTCHA_image.asp,line 864
my enviroment is apache+iasp

oh my test web is http://sunmuse.gicp.net/test/CAPTCHA/CAPTCHA_image.asp

thx, !!!!!! i see!