SEOMike - 9:54 pm on Oct 14, 2008 (gmt 0)
Does it mean Google no longer has the original linking page in its index or is it more complex than that ?
I suspect that these are pages that Google discovered through spidering & indexed but never found any external links for them. I see some pages in WMT from directories that I specifically told GBot to stay out of but the pages were discovered nonetheless. The pages were one-off things for friends and never had any links to them from anywhere. That's probably why they say "unavailable."
Is Google guessing at pages on my site ?
Probably. GBot will do that sometimes in order to determine how your server responds to random queries.