Just wanted to add my 2¢ re: this issue with Wordpress and say that the same issue is also a problem for Drupal. Whenever I go to update a module, I find that I can't delete all of the old version's files because WinCache has a lock on them. I did discover today that I can use wincache_refresh_if_changed to manually unlock the locked files one by one, but that's not a great long-term solution.
WinCache has dramatically improved the performance of my website, so I'm going to deal with this issue the best I can for now and keep my fingers crossed that it gets resolved via an update soon!