You might have it jacked up too high(over the fulcrum point)..try giving the jack a little jerk toward you(pulling on the handles), then try the release pedal...
Be sure to have someone steady your bike during this process..
You must have a different kind of jack.
Not sure how it affects this kind of jack, but when I removed the front wheel, the weight did shift to the back big time. It looks like one of the lift saddles is bearing more of the load.
dexterdave was correct even though his jack is different. I must have jacked it so high that the weight of the bike was holding the lock lever down. Because it was all the way up, I could not lift any higher to get weight off lever. To solve issue, I used a second hydraulic jack to lift the back end higher then had 3 friends help lift it a bit higher to pull the jack out.
I don't believe the jack is broken, but I would advise A: make sure the bike is level and B: try not to lift it so high.
It wouldn't surprise me if the frame twisted so much, that somehow it got bound up. When it is down off that thing, throw it away and get a J&S. Problem solved.
Get a J&S jack, and your troubles will be over. I have 3 buddies who borrow my jack often because they HATE their jacks. 2 of them have craftsmen jacks and the other has one he got from Harbor Freight .The J&S requires no straps, and will also fit all Dyna Frame bikes without needing the plastic spacers, Shims etc.. Best purchase i have made since buying my Harley .
That doesn't help him much with his problem right now though does it. Also, many people have the Yellow Craftsman jack including myself and have no problems at all with it. So why spend a whole lot more money on something that isn't used that often. JMHO
OK, maybe a stupid thing, but you did close the release valve all the way, didn't you? If that's open you obviously won't be able to jack it back up to take the weight off the lock lever.
Do a google search and try B2 products (motorcycle lift). I have 2 B2 stands and they are second to none. You can even get them in HD black and orange. I wish I had some pics. If I get a chance I'll post some later.