Hello John
I'd be curious to know what training has preceded this. Whether, for example, you did the offseason that might be required, perhaps the strength component of the training, and also the speed-stamina. It's impossible to say exactly what hte problem is, of course, and I'm sure there are many opinions you'll hear (and most will be valid!), but what can often happen, in my experience, is that a runner moves too quickly from the base phase of training into the speed/sharpening phase, without consolidating the stamina/speed endurance in the transition phase. And so then you end up with a situation where you can probably run a pretty good set of 200's, and maybe you feel great on your easy days and your tempo runs, but the ability to run at 90% of maximum for medium duration is compromised.
So my advice would have been to do a period of running where your quality day is something like a 3000/5000m runner would do - 6 x 1000m at 5k pace, or 5 x 800m at 3000m pace, or even 3 x 2km at 5k pace, because that's proviing the necessary strength component. You may well find that you have the speed and you have the endurance, but the race situation exposes a critical gap.
This was the case for Mulaudzi a few years ago (the SA 800m runner, silver in Athens). He had awesome 400m speed, and his longer running was great, but his 600's, 800's and 1k sessions were weak. So a period of consolidation and he developed strength and speed-endurance, he was good to go.
One last thing, if all this is fine, then overtraining is ver likely - if you are not rested on the start line, then 800m is about you'll have in you. So maybe you're over-racing having not reduced the training volume quite as much as you need to.
Good luck!
R