Thanks, Michael. I believed you the first time. :-) I have more than a dozen blogs, each with different themes and plugins. It'll take me awhile to determine what the constants are among them all.
I thought I'd resolved any memory constraints via this thread, and indeed, any slowness or errors I used to experience are gone:
But I'm still getting reports from DreamHost about using too much memory, even though my resource usage graph displays an average of around 20 MB, and I have 885 MB allocated:
Your DreamHost VPS has just exceeded the memory allocation that you've established. If left unchecked that behavior could begin to negatively impact the VPS services of every other customer on your server.
As a result we've had to reboot your VPS, effectively restarting your virtual machine. You may experience several minutes of downtime while your services come back online.
Based on the usage pattern that we've seen today, it's clear that you'd be best served by either working to reduce your memory footprint or simply increasing the amount of memory available to your VPS.