What kind of authentication are you using? Depending on how you have IIS set up, your scripts may be running as a default web user with a name like IIS_user or something like that.

Have you run your script from the command line as the default web user? Does it still work when you do so?

Until I wised up, I often had a problem with scripts which ran from the command line but not as a web program. In every case I can recall, the problem was that the default web user lacked the rights to run the script correctly. When I fixed the rights issue the problem went away.