Re 1.5 to 1.5.1 upgrade...
I found I had to replace the template-functions-links.php with the previous 1.5 version of the that file.
On the index page the "previous" link was spitting out /php/php?/paged=2 and this applied to a variety of themes.
It now operates fine with "/index.php?pagd=2" using the 1.5 file
Note, this is on a development server and not live :)
Any ideas why this would happen and am I devaluing the installation by replacing this file with the previous one?
Apologies as this was posted in the pinned upgrade thread but got swamped by an animated discussion.