Ideas about cause of pugs collapse/shock episodes

This is a long shot as I've seen countless specialists but I thought I'd see if anyone on here may be able to read about what's happened to my pug and have ideas that maybe we haven't come up with.
In June 2008 my 5 year old pug went into shock or collapse- she was non responsive, gums gray, temp. 97*, blood pressure dropped. We were able to get her to the E-Vet in time and they barely saved her life. The vet and her allergy specialist thought she must have been stung by a bee and gone into anaphylactic shock. After this I kept her inside 100% of the time. Then in December 2008 it happened again. She went from barking at the TV to completely collapsed and non-responsive in 15 minutes later. We were once again blessed enough to get her to the vet in time. However, we were then totally lost as to what the cause was as she had no access to the outside and I had been with her the whole morning- no bees!
They tested for addison's and that was negative. We then went to UC Davis and they ran every test they could think of- ultra sounds, x-rays, cardiac tests, blood work. Everything came back perfectly normal. She has not had an episode since December 2008 however I still don't know what caused it and still cannot leave her alone- she has had a "babysitter" 24 hours/day since the second episode and I still set my alarm to wake up once an hour throughout the night. The vet at Davis can't come up with anything and thinks I'm crazy. But, I just cannot leave her alone until I know she will be okay.
Anyway, I just found this place and was hoping someone may have had a similar experience or might have some thoughts about what else to look at.
Thanks!!!

[Thomas Dock, CVJ, Vet. Technician]

How scary these events must have been for you!

I would suggest that you copy and repost this question in our Ask A Vet expert forums.   We have more than 30 very smart DVMs from across the country who may have heard of a similar situation or may have an idea of what might be causing these episodes.