Hi !
Oh, I also tried using just mongrel_rails cluster::restart, but files seemed to keep getting served out of the PREVIOUSLY current folder (the one in which Mongrel was initially started).
I can't remember where I saw that, but Mongrel finds the real directory from which it is started, and attaches there.
What you have to do is use the -c switch when you configure your cluster:
mongrel_rails cluster::configure -c /var/www/mysite.com/current <other config options here>
When the other cluster tasks read the config file, the first thing Mongrel will do is CD to the directory in question. So, the symlink will be refreshed.
Hope that helps !