I am having the same issues. Fresh install of Windows Server 2008 SP2 fully patched running IIS7. I used the Microsoft Platform Installer to install PHP MySQL and the wordpress blog. Then I restored a previous blog from backup that I made before I re-insalled the OS to try and fix this issue.
IIS seems to be caching something because I can updated the plugins if I restart IIS right before I do the upgrade. If the site has been active for a while trying to upgrade the plugins gives me the same error you have above. Checking the directory shows a phatom folder that cannot be taken over or name changed or anything. Cycling IIS will release these resources and the folders completely disappear and then I can install the plugin again.
It seems like IIS is holding some sort of cache on the plugin resources so when they are deleted by WP IIS doesn't know what to do and just locks those resource names so you cannot finish the update.
I never ran into this in previous versions of WP but the platform installer also adds other items like cache dependencies so it might not be a WP issue at all and could be some other piece installed by Microsoft that is causing this blockage.
I have a feeling more people will start running into this and I hope someone out there is listening.