Directory Service Failure; Can’t Login

Running OS X Server 10.2.6 on a 1ghz XServe file serving only, no other services running almost daily, and sometimes multiple times a day, all users lose the ability to login to the server. the only solution is to ssh in and kill directoryservice. once it restarts everything is fine for anywhere trom a few hours to a few days. this problem has plagued me since installing the server in Dec 02. I keep hoping one of the incremental upgrades will fix it. If I could fix this, we would have no problems at all with the server. Any ideas or suggestions. Something need to be reconfigured? Anything?