I have an ASP page that calls a FOX DLL

ASP CODE:
Dim strjobnum, strbinnum, oNB, strBinResp
strjobnum = Request.Form("jobnum")
strbinnum = Request.Form("binnum")
SET oNB = Server.Createobject("filmroute.fwip")
strBinResp = oNB.binjob(strjobnum,strbinnum)
SET oNB = Nothing

Once this is complete and I try to regenerate the Multithread DLL I get File access is denied. In order to regenerate it I have to reboot my PC which tells me it is still loaded in Memory. Shutting down the COM object through IIS does not help as well as shutting down the web server service. I found an article on this and all variables in the COM object must be PRIVATE which they are. I am woried that I will run out of system resources. Does anybody know why it is still in memory and what I can do to fix it?