Find where googlebot follows its links from?

Webmaster tools maybe?

[futureX]

Hey, I'm in need of a little help, looking in my webmaster tools I can see a lot of requests coming back 404 of pages that dont actually exist, and are infact very similar to my actual URL scheme, for example;

(obviously use a mod_rewrite)

The actual url scheme;
[domain.com...]

What goole is looking for (404);
[domain.com...]

I have checked every link on my site, sitemap is fine I cannot find where google could possibly have followed these links from, its not one or two either, its 404'd almost all of the articles on my site (i still have pages indexed under the correct scheme).

The only possiblity I can think of is that when working out mod_rewrites (after the fact =/ ) there may have been a couple of minutes where the link was wrong (only minutes) possibly google picked up the pages during one of these small windows, but google has tried to spider the pages 3 or 4 times a week or so apart.

Does anyone have any tips as to where I might be able to look...