I took minapple's advice and it worked! ... forum pages ... were url-only in the serps. ... the meta-description and the h1 were the same for all pages. I deleted the meta-description and changed the h1 ... now in the serps with title, snippet, and cache.
Of 15,600 my-site-only SERPS, just 400 have title, snippet, and cache. After a quick check on the page source of a handful I can confirm that *all* 15,200 url-only SERPS have unique meta-description + h1 title (the php-coding was designed explicitly to do this, and the actual page source confirms it).
(With just one caveat) perhaps of more influence was the fact that the header text **changed** - just that, it changed.
The caveat: all of the pages on my site can give identical header + body text under 2 different urls:
The only difference is that the first delivers a gzipped-page and the second delivers a non-compressed page. Doing an open-search for the title of one of the url-only SERPS (http://www.google.co.uk/search?q=+%22USR+56k+Gaming+Modem+PCI+5613%22) delivered up the non-compressed variant, but not the compressed link.
In addition, the site was--some years ago--with a free-host; to prevent 404's, that host re-directs to my site, so