It does have the look and feel of something that doesn’t finish booting due to some race condition and locks up specific cRIO resources. Once you break free of it, everything is fine.
Some services are blocked or slowed while others remain unimpaired.
Probably, due to specific resource conflicts.
I would hazard that it isn’t cRIO CPU overhead though, since some low-priority services (ftp) sometimes work. Those are the first to fail when there’s a CPU shortage.
The 4-flashes might indicate that memory isn’t being released by something that sucked it up, then doesn’t complete and just sits there. Maybe two boot tasks asking for a combined 110% of memory at the same time, then waiting for the other to give up first. Sort of an OS hydra staring contest.
One thing to test, if it happens to any of us again, is to run the LabVIEW System Manager and monitor the CPU and Memory usage for clues. Do it before attempting to download or do anything else, while the 4 flashes are occurring.
If anything significant happens take a screen shot and post it for the rest of us.
