Truly odd one:

As of about two hours ago, 100% of my shares are being reported as stale..I am using 11.5 and had at most 40% ever, with fewer since 11.4/11.5 updates until then.

Niw I am actually seeing more reported stale than submitted, like the 9 or 10 sales with 8 total for a single card? Weird, but consistent for nearly 2 1/2 hours now.

I am single mining on ethermine.org

PS: (Post Mortem)

As always, I should have done a bit more research on things. I just got my first cup of coffee and didn't look at basic things like the reported share acceptance times. Watching more closely for a few minutes showed numbers like 5000ms or more than 5 full seconds.

I still have not pinned down exactly why it was, but since the rig had been running Windoze 10 for 18 days, I used the reboot method of fixing the problem and the times went back to being consistently under a second.

For me out in the middle of the national forest 20 miles from the closest true high speed internet, I'm on a satellite link, so the fact that I don't get under 50ms is normal. In fact 500ms is low for me and 750ms not unusual due to the propagation delay inherent to satellite up links and downlinks.