OK, so maybe not EIC --- this isn't much of an update since I haven't been in yet to our hands-on vet, but while researching Exercise Induced Collapse, I emailed a DVM in Saskatchewan, BC who specializes in this, and I thought I'd share her reply that offers several things to consider. (I've mailed this in to my vet to add to the 'data' we're collecting on Ruby - we are going in soon on a nice WARM day to try to trigger another episode).
Thanks for the new link to the videos -this time I was able to watch Ruby's episodes.
This is definitely not EIC. I think it is most likely that these episodes represent partial focal seizures. It is important, however, to have veterinary evaluation to rule out things like low blood sugar, electrolyte or calcium abnormalities and heart disease with an intermittent heart rhythm problem (causing the heart to beat much too fast or much too slow periodically making Ruby dizzy). Also transient ischemic attacks (mini strokes) have been reported to cause similar symptoms in dogs so evaluation for predisposing causes (high blood pressure, kidney disease, heart disease, hypothyroidism)would be worthwhile.
If all testing is normal it is also important that a veterinarian perform a complete nervous system exam to make sure that there is no evidence of brain disease in between the episodes. Also they should look in the ears to make sure they are ok. If everything is normal then I think it is most likely epilepsy.
In that case I would probably try treating with oral anti-seizure medications (like phenobarbital) to see if this decreases the frequency of the episodes.
We have evaluated quite a few dogs with partial focal seizures looking a lot like Ruby. Some dogs progress to have regular generalized seizures over time but others do not.
I hope this helps. Let me know if you figure this out or if Ruby starts having more specific localizing signs - I will keep a copy of the videos and it would be nice to know what she does actually have.