Redmine

Hi,all
my version is:0.8.x ruby 1.8.6, 1.8.7 Rails 2.1.2
os: windows server 2003
db:mysql 5.0.27
ruby-aware server: i'm not sure,somebody else installed it,and he's not here by now. i guess maybe Mongrel if he followed the steps described in readme.txt in rail directory.
and my question is redmine seems not stable, especially when many people(10 up) work on it at the same time(usally all i do is creating or updating an issue etc). web server cant response.
i tried to restart redmine service or mysql service, but it didnt work.after i restart the machine. everything is fine. what should i do? has someone else meet this problem before?