Hello,
I have changed all of my pages on my websites to SEO friendly URLs. I noticed the increase on Page rank on some pages. However, there are more errors of pages not found on my log.
I have changed from /index.php?id=1234 to /index/i-like-this-forum/.
So, my question is, does anyone notice the same thing?
Does my SEO pages affect Google page rank?
Thanks a lot.

Nope.

As soon as you change URLs you "break" any PR (real or imaginary toolbar version) and you "break" the indexing of the pages. Provided you have use a permanent redirect (301) it will catch up again. Usually it takes 4 to 6 months for it to stabilise again.

BTW what is a "SEO page"??