The error message "Insufficient System Resources" is reported to Domino by the Operating System and it indicates that an Operating System resource is nearly or fully exhausted. The most common resource that message refers to on a machine running a Domino Server is the Paged Pool (a section of kernel memory). The error is also sometimes, but not always, reported in the Event Viewer Logs.
When the error refers to paged pool issues, it begins displaying when 80% of the paged pool is consumed. If the paged pool is actually exhausted, this often results in widespread database corruption on the server as well as issues with Domino server performance, hangs and/or crashes.