I know this is an older post, but if anyone else is looking this up, let me chime in and say I've had the same experience with the Wyeast 2565 and 2575 within one week of each other. I made two all-grain batches with ~7.5 pounds of grain and a pound of honey. Airlock didn't bubble first day (but it was definitely fermenting as my nose can attest); it then had a "yeast event" and I had to put on a blowoff hose. After that, I kept it in a cooler spot and it slowed to a crawl and developed a sulfur odor. It also dried out to 1.004 (holy crap!). Second batch had similar behavior without the "yeast event." For those of you waiting to take it out of primary, I would recommend taking it off primary after a week to at least get it off the residue from the hops.
I'm hoping this will be okay after secondary and conditioning, as I made it for my sister's wedding.