The next page link doesn't exist on the 2nd album page. The next page link shows up on the first page within an album and on the 2nd album, only the previous page link shows up. I have to manually type in the page number to get to the 3rd page.

Any thoughts?

Sorry, but this is scarce little information to go on.

Custom theme? Version of Zenphoto? Any other relevant information (like how many albums are there, is this the gallery page you are refering to? etc.)

Sorry, was hoping this was a possible known issue.

Theme: stopdesign (I changed it to default and the issue still exists)
Version: 1.2.5 [4022] (just upgraded)

Set to 9 albums per page, with a total of 27 albums. The 'prev page' link show up on the 3rd page and does point to the 2nd page, but there is no 'next page' on the 2nd page.

Sorry, I am not seeing this issue. Maybe you can try the 1.2.6 release candidate and see if the problem still exists.

which php file controls this feature?

nm, weird. I changed the number of albums per page to 12 and the 'next page' link shows on the 2nd page. If I change it back to 9, it still doesn't show. So I guess 12 albums per page is what it's going to be.

There may be a CSS issue. You can look at the page source and see if the link HTML is present.

Anyway, the controling code is on the gallery.php. Look for hasNextPage().