I would like to know how scalable is JRun4?

We have been using JRun4 for quite some time, but it suddenly behaves erratically - once the server is restarted it works normally.

We have about 9 applications (simple applications) running on the server. I wonder is this the cause of problem.

The applications consists of mostly JSPs and few servlets. There are a few EJBs, small ones.