I believe I've found a conflict between IMSC Rapid Mailer and Quick Cache.
If I have IMSC Rapid Mailer enabled then Quick Cache doesn't seem to be able to generate NEW cache pages. If there is a page already in the cache then Quick Cache will serve it up. But if the page doesn't exist, it won't create a new cache image of it.
I base this on looking at the bottom of the page source for the Quick Cache text.
If Rapid mailer is enabled and I go to a new page, that page never has the cache indications in it and nothing I do seems to get the page cache created.
But if I visit the page with Rapid Mailer disabled, then I see the cached page indicators. I can then enable Rapid Mailer and visit the page and I still see the cached page indicators. So that is telling me that with Rapid Mailer enabled, new cache pages will not be created, but any previously existing pages will be served.
So how do we determine who has the problem / conflict? I certainly am not qualified to look at it to determine what / who has the issue.