Safari refusing to open https

2011 mini
Lion 10.7.1
Safari 5.1

Not a single problem for weeks, and now out of the blue, Safari won't load https sites. No beach ball, no feedback in Activity Monitor, just stops loading webpage content. If I cmd-W the offending https window it will disappear leaving the other windows however they are still unable to load new content. If I cmd-Q and relaunch Safari the resume feature perpetuates the problem. However if Safari opens anew at a regular http site, things go back to normal.

Much less frequently regular sites will cause the same problem, but a quick app relaunch and the once-stalled page loads instantly via resume.

Firefox is unaffected. Other Macs on the network are unaffected. If I bypass the router, the problem remains. Resetting Safari via the menu didn't work. I'm at a loss. Google failed me on this one, which is why I'm posting. Any help getting restored would be greatly appreciated. Thanks.