I'm pretty sure Frederick isn't going to like me for this mess! LOL!
I'm pretty sure this is a site issue not a w3tc issue but I don't know where to start.
My site has always been extensively resource heavy, to a extreme degree, even after having been looked at closely by four of the core dev team at Savannah WordCamp.
We moved it to a virtual machine, using memcached, to isolate it because it crashes just about everything else. W3TC has become a plugin I absolutely depend on to keep the site up even "most" of the time.
I'm an extensive beta tester and somewhere between 3.0 and 3.1 stable, I picked up a "minor" problem that I became aware of after rolling on to 3.1 stable, that of missing the pagination for the page in wordpress that lists all posts. (In the middle of that beta I also lost the ability to write php errors only to log and not to screen, in the manner I had been doing for many versions, and we've since had to try to come up with other workarounds, but no one on the beta list seemed to know what I was talking about.)
Deactivating all plugins (except maintenance mode) and rolling the theme to Twenty Ten or Eleven does not fix this.
About this time site stability took a small turn for the worst, but I was struggling with some family stuff and did not hat time to debug.
A couple weeks back (actually closer to a month now), one of the upgrades to w3tc started interacting with something my site is doing and caching all the wrong stuff.
Also at the same time, my cloudflare + maxCDN settings started conflicting and suddenly if I had them both enabled, the site flat out wouldn't load front end. This happened immediately after a w3tc upgrade but I'm sure from reading notes from maxcdn that I didn't have this 100% set up right in the first place. I was able to get to the backend but not the front end, and I disabled maxcdn at the time (unfortunately).
Regarding the prior paragraph about incorrect caching, if I went in to write a new post, in the new post editor. It might cache the page at the first sentence, and when I hit save draft, the draft save would be the cached copy, not the now several paragraphs I'd wrote. I started disabling w3tc every time I wanted to write a post. Writing, publishing and then re-enabling.
I know I should have been in here looking for help then. It was also caching plugin upgrades and would cache somewhere after the upgrade but before the activation, so that even though the upgrade progress said the plugin was reactivated, once I cleared the cache, it was obvious the newly upgraded plugin was not activated and I needed to activate it manually. This gets old after a while.
There's other admin related pages being cached too but those are the biggest ones.
Today I found myself getting a 500 error only on wp-admin/post-new.php and chased that back to "Yet Another Related Post Plugin" which I just deactivated.
Theme is a css-changes-only child theme to twenty eleven.
Current active plugins are:
Google xml sitemaps
Social (by Mailchimp)
WordPress SEO (by Yoast)
Recently (and usually) active: Premium Slider, SEOPressor v4, YARPP & W3TC.
I'd be happy to provide a w3tc settings export (or site access) though I don't want to link to that settings export here since it contains my cloudflare api key etc.
Even after removing YARRP today, reactivating w3tc still presents me with caching trouble in post edit page, and makes it nearly impossible to compose a post without deactivating it.
I'm uncertain if the pagination issue on wp-admin/edit.php is a big deal or inconsequential but I felt it necessary to include to paint the big picture.
Any feedback, thoughts, or advice?
PS: If I'm slow replying back its because I have to leave my main browser to reply. Firefox has picked up an annoying tendency to auto-case-correct my username for the forum (I hear others are having this issue with other sites) and because the UID here is case sensitive I have to log a different browser just to reply.