2.7.1 Upgrade with IIS Permissions

I have been running WordPress 2.7 successfully on an IIS machine for a few months now and was just prompted to upgrade to 2.7.1. If I try to use the Upgrade function in the Admin Panel, it gives me several errors about unlinking and not having permissions. If I add permissions to Modify and Execute in IIS (I’m using Plesk, specifically), it goes through OK but it leaves the .maintenance file in the root. If I leave them as Read/Write/List then I get these weird errors about files named with just numbers, the .maintenance files stays in the root and it always tells me that the install succeeded but then I get a message right after that it failed and I need to try installing again. Any ideas about what permissions I need on what folders? All the docs deal with CHMOD values and those don’t apply to a Windows box… 🙁