I'm another fan of single-page reviews as I find it easier to scroll to the specific info I'm interested in than jumping from page to page. Many thanks for asking! :)
If you have the time and budget, I highly recommend buying (or checking out form the library) Lee Frost's "The Photographer's Guide to Filters". Lots of info on filter systems and how/when to use ND...
I don't have the FZ7, but had the same problem last weekend with my FZ20. Hadn't happened before, hasn't happened since, so I've no idea what could've caused it, but if it happens again I'll take...