I've been using Fireworks for the past 5 years or so for heavy prototyping work. Have loved it! Once I moved to Mac OS Lion 10.7.2 I started having major problems with the software. It was getting progressively worse - from a crash or two per day to a point when it crashes on 'save', crashes on start up, crashes every 2 min, irrelevant to what I'm doing, which means I cannot have any work done!!!! I'm aggravated beyond belief: looks like Adobe have dropped development for this product as there's no fixes or patches, 5.1 hasn't been updated while every other soft in Creative Suite has been upgraded to 5.5. This is such a shame, as Fireworks occupies a rather unique niche for designers and I've worked with it quite successfully for so many years! But they don't leave any other option and I have to have work done. Will probably move on to using Omnigraffe, as many others aggravated by constant bugs and crashes under Lion.
Sorry you are experiencing these issues. A reinstall might help, and you can also check out these technotes from Adobe.
Rest assured, Adobe has NOT dropped support for Fireworks. I would also point out that neither Photoshop or Illustrator received a 5.5 update either. The main products updated in the 5.5 release were Dreamweaver, InDesign and Flash.
I had looked at these resources already, nothing has helped. But thanks for posting!