In most cases where it appears that a cache refresh has not worked, the problem is simply that your browser itself has cached the page(s) you are viewing. This is typical with IE, which caches pages aggressively. If simply moving about your site normally doesn't show the changes, try emptying your temporary internet files.
However, on very large and/or active sites, this issue can be seen because the reset cache is "queued" for later operation when there are no templates in use. This can take quite some time if your site is very busy. If you just can't wait, then shut down and restart the server.
Also depending on the activity of your site and exactly what it is your templates do, a cache reset could make it appear that your site has stopped working for a (lengthy) period of time before it starts responding again.