The web sites in question are hosted by Host Gator and Wired Tree. Usually code friendly, but?
Unfortunately I am not a coder so I would not be the one to code a solution.
Is one potential solution to just deactivate WP Super Cache? These are not high-volume web sites so we are not talking 10s of thousands of htis/page views a day. Fast is obviously always better, but I think the sites could survive w/o the caching. Would this solve the issue?
Or, if nothing else, de-activate WP Super Cache and test to see if the issues go away? I think on one site I have the Super Cache code inserted into the BPS box where its supposed to go, but, the problem still persists — which may corroborate your conclusion that its between WSPC and WP. Its just strange that I never seem to run into this until I installed BPS on all the sites. Been building WP sites for years and past sites with WPSC years ago seemed to run ok.