FM 5 Server Quits On Its Own

[harold]

We just upgraded to FM 5 Server and it will quit on its own, seemingly at random. We'd successfully run FM 3 Server on an old iMac for a couple years (and a PowerMac for years before that.) We have 9 users max at any time. The error message we get is -1070. We've tried everything: switching from AppleTalk to TCP/IP; recovering each file in 3 then cloning, converting to 5 and importing; reinstalling the server; buying new iMacs to replace the older power macs on the network (though we still have 2 power macs in use). Please help!!!