Very simple solution.  From your Windowsn Start menu, select Actian PSQL12, PSQL Control Center and Documentation, then under Common tasks in righthand window, select Configure Microkernel Router, the select Performance Tuning, and uncheck the "Use Cache Engine" box, then click either OK or Apply.  Works like a charm.   Patty

now what?

cant restart engine and the system is not functioning at all

Why do you want to restart the engine?  Do you mean the cache engine?  Because it should not be restarted.   My steps in a case like this would be to reboot the computer with the error, Follow the steps outlined in my earlier e-mail to be sure that the "Use Cache Engine" is unchecked, then start Sage Construction 300.  In our experience, this worked on our peer-to-peer computers without any problems.  Further issues, you should either contact your Sage Partner, or Sage support.  Good luck. 

Marc,
You want to be careful about turning off Use Cache Engine depending on the applications you are using.  You indicate that 2 of the 3 clients are using a Server version engine (has both the Transactional and Relational services).  An easier answer would be to add the Server version engine to the 3rd computer.  I'm guessing that you or someone you know would be able to complete that (given that 2 already have it), but if not I would contact your Certified consultant (this should be a 15-30 minute phone call unless the workstation won't allow a straight-forward install.

There are multiple other configurations that you could attempt, but I've found this to be a quick solution.