‘doh! (smacking self in the forehead)

Now I feel bad for not taking a careful look under the hood when the problem first occurred and jumping to the conclusion that if the engine cranks fine but the engine won't start, it must be the crank sensor (or the fuel relay, as I later learned).

I went back last night to put in the fuel relay, but before I put that on I thought I would shake the crank sensor a little as recommended above, see if it would work. While I was looking for it I noticed what looked like a spark plug wire hanging, unattached to anything...

Yep, the coil wire had fallen off of the bottom of the distributor cap. I put it back on and the car now runs fine. That's all that had happened, the plug had fallen off.

Thanks for your everybody's help though, I’ve learned a few more things about my new Volvo (one of which is to not assume anything and always give a careful look over), and will learn even more this weekend when I put on the crank sensor I’ve already bought (it needed to be done anyway). Thanks Brian S for the picture, I now know where it is.