[support] Drupal 7 catastrophe

[Roger]

As I understand it Drupal loads all modules and the current enabled 
theme, (or maybe all the themes) on start up.

More modules = more memory, even though many modules are on call, not 
used in development or production except in certain rare circumstances, 
for example norequestnewpass, newsletter and it's associated modules, 
nat, mailsystem, autonodetitle, backup_migrate, devel, and all  
workbench modules, just to name a few. For one of our sites, 43 modules 
in all. Most of those exist only to solve issues introduced by other 
modules.

Because the Mayo theme does not easily lend it'self to newsletter 
creation I installed LayoutStudio with intention to build a suitable theme.

Now here's the cruncher.  I had ini_set('memory_limit','-1'); as an 
experiment in settings.php to overcome the dreaded memory allocation error.
Development of the new theme went ok until for some reason, out of the 
blue,  Drupal suddenly started consuming all of the pc memory and 100 % 
cpu processes, grinding the machine to a halt and running the hard drive 
red hot.

I rebooted, emptied browser caches, ran "drush cc all" in the drupal 
directory, drush ground to a halt, taking 7 minutes to clear caches. 
Rebooted, ran mysql TRUNCATE on the cache tables,  but on opening the 
127.0.0.1/myfile, within 3 seconds all memory was used and the pc 
virtually stopped. No pages open. Mouse and keyboard also virtually dead.

Rebooted again.
In settings.php I put ini_set('memory_limit','128M'); and the memory 
allocation error again displays, will not open the site, now fails to  
to allocate 72 bytes, no matter if I set it at 32M, 64M, 128M, 512M or 1024M

There are no helpful error messages in the system, in /var/log 
or/httpdor in the php_error file generated by php.
I believe Drupal has written something into the database because if I 
use that drupal system with another similar database the error is not 
there. Seems to be because we were developing the theme.
Are there any known issues with Drupal module LayoutStudio?

Google is of no help about XCache or eAccelerator but said something 
about installing memcached which I did but  that's no help.

My other Druapl installs seem to work fine.

Google reports that when the memory consumption error occurs the only 
recourse is to delete Drupal and the database and rebuild from scratch.
Roger
I would love to solve this but am perplexed where to look and what to do.
Thanks in advance
Roger