On one of the SharePoint 2007 servers that I support, we started receiving intermittent Internal Server 500 error messages. Upon further investigation, we found that in the ULS logs we were receiving the following error message repeatedly:
[shell]Server Out Of Memory There is no memory on the server to run your program.
Please contact your administrator with this problem.[/shell]
After an IISRESET, the issue would go away for about 20 minutes and then it would come back. In monitoring the worker process memory utilization we noticed that it would jump from 200/300 Mb of utilization to over 1 Gb of utilization. By using the suggestion in this article, we found that the issue was caused by having more than 50 links in the quick launch navigation. Granted, we know it is not good for usability to have that many links in the quick launch navigation, however we do not control that for this site.
To resolve the issue, we needed to change the SiteMapProvider setting on the Master page. To modify this, open the Master page in SharePoint Designer. Change the following line:
Once we made that adjustment and did an IISRESET, the issue no longer existed. Hopefully if you are facing the same issue, this helps you out.