I once had my subaru raised on two jacks (changing the front brake
pads) and it fell over on me (yes, it actually fell on ME!). I
literally came about 1 inch from loosing my reproductive organs under
the front brake disk. It pinned the crotch of my pants to the ground
and scared the heck out of me. I started screaming and my roommates
came out and lifted the subie up off of me.
Another time I had a '72 bus jacked up on one side and was again
doing brake work. The jack actually twisted and the whole bus fell
down. It fell kinda slowly, so I managed to get out of the way, but
after those two experiences, I learned NEVER to work on a vehicle
that is only supported by jacks, and to ALWAYS chock both sides of
ALL the wheels that will be staying on the ground when I jack things
up. To lift the front of my Vanagon, I just jack up one side real
high and put a jackstand underneath, then jack up the other side and
do the same thing. It really isn't safe AT ALL to have two jacks
holding up the entire front end, rear end or side of a van or any
vehicle for that matter.
Good luck,
Joel