I have discovered that when I first (eventually) login as an administrator, the very first time I chose to
edit a text/html module I receive an error message;

A critical error has occurred.
Object reference not set to an instance of an object.

If I  go back a page using the firefox 'back' button and try to edit the same text again, not only does the
edit work this time,but the whole site mostly works thereafter, during that session. I say mostly because
there are still times where if I choose to logout , the site hangs. During this time when I use task manager
to review the processes, WebDev.Webserver.exe jumps in memory useage, off the chart. Normally, if the
site is running OK, memory usage is ~500MB. When trouble strikes, memory usage jumps to ~1.2GBfor the PF Usage.

There must be hint in this somewhere???

The module is causing the performance issue.  Remove it and recycle the host installation either through Host - Settings or simply edit web.config and add a space to a comment and save.

You will need to investigate the events module... Not knowing enough about your install I would for now remove the events module from the page and see if your performace improves.  I would review the error logs for new errors...

Next  I would either reinstall the events module and check the logs and related SQL Sprocs.