Sat Jan 10, 2015 11:49 am by bob
That implies that there is something else going on which is chewing up your available RAM, or you do not have enough to support the number of clients you are running.
If you look at the Task Manager (right click your Taskbar, select Start Task Manager, Processes tab, sort by Memory (Private Working Set)), what is taking the most other than WOW. Also how much are the WOW instances taking?. You may need to select the "Show processes from all users" button.
May also be worth taking a look at the Performance tab and checking the values at the bottom, like Physical Memory -> Available, Kernel Memory -> Paged, System -> Commit (or a screen shot).
Also, that diagnostic?
Have you tried rebooting?
edit: and it may be worth unloading all WOW addons (other than ISBoxer of course) if it seems like WOW is the culprit.