Get a new server, or atleast up the RAM. I made the jump from 2GB RAM on the server to a new server with 8 GB. I use to have the same problem you described with needed to reboot the server everyday! Haven't had to since the new server. You might check your current server memory usage stats. Sometimes something can become corupted and it will demand more of the available RAM.

Tom Young, DO
Internal Medicine Consultants, PC
Creston, Iowa