OK - I now see at least part of what happened. Things had started to go up, but temperature cooled a little, and power dropped a tiny bit, then they really dropped.
I just checked the folding - I lost the work unit - unstable machine and she's started a new one. :-(
14:21:35:WARNING:WU00:FS00:FahCore returned: UNSTABLE_MACHINE (122 = 0x7a)
14:22:44:WARNING:WU00:FS00 : Detected clock skew (1 mins 09 secs), adjusting time estimates
14:33:29:WARNING:WU00:FS00:FahCore returned: UNSTABLE_MACHINE (122 = 0x7a)
14:34:37:WARNING:WU00:FS00 : Detected clock skew (1 mins 07 secs), adjusting time estimates
Sun :-)