1)I confirm that the problem is not with the service itself, because when I stop any of the 18th running services I can start any stopped service
2)Intel Xeon CPU 3.4 GHz 3.5 Gb Ram
Microsoft Windows server 2003 Enterprise Edition SP2
3)I attached our xml, but as you can see the configuration are almost default, and the problem occurs on any .exe file that I try to start under an user account. If I try to run under localsystem it starts fine.
P.S. After the last system boot the number of services that I can run under user accounts simultaneously increased from 18 to 19, therefore the problem occurs when starting the 20th service. The services under localsystem do not affect the maximum number of services under user accounts.