In answer to my own question:
Settings
Prefs
Security
Ignore SSL Errors.
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Is this secure for Ebay and the like?
You should only enable this option temporarily, as if this option is enabled any certificate will be accepted. This will make it possible to perform
man-in-the-middle attack, even when SSL/TLS (
https://) is used.
I think Fab is considering adding per site preferences to OWB, much like in other browsers. Then you could allow the self-signed certificate for the specific sites alone.
I wonder though, what did you do exactly ("I turned on my cache and all that jazz") to when you began to get these problems for valid certificates? Maybe OWB doesn't work correctly with certain kind of proxies?