Google Adding .html to my php pages?

[Miop]

Some of my site pages appear twice in Google - once as the correct page e.g. domain.com/section.php/1/0
and again as domain.com/section.php/1/0.html.
(they are treated as two distinct cached pages)

Anyone any idea why this may be happening?
These pages certainly do not appear in MSN or Yahoo so I'm guessing it's a problem with Google and not my site.

Thanks.

[encyclo]

Do both URLs resolve to the same content? Are you removing the .html extension with mod_rewrite or similar? Have you changed your URL structure from extensions to extensionless URLs?