Installed v4 (non-beta, on 10.7.4) - still the same issue - disconnects on subsequent connects. Starting from v4beta Vine was unusable until I put this line in my ~/.profile:
alias rvnc=‘killall 9 “Vine Server”;osascript -e “tell app “Vine Server” to launch”’
I connect to VNC over ssh tunnel, so need to ssh in anyway, this way the first thing I do after logging in is type rvnc and then I can connect no problem.