[Chuck S]

You using the same photopost versions?

this would have nothing to do with an import that happens months ago.

The variable {$cats['thumbnail'][$x]} is defined in pp-inc.php in the catrow function so I would suggest if you want to compare apples to apples you ensure your using both the same versions on those two sites. However as I noted the variable is controlled by $lastphoid which is simply the photo id that is the lastphoto uploaded to the cat and in your case since the galleries in question are parent categories the lastphoto uploaded field will be populated by the last photo uploaded. Try uploading a new photo to one of those children categories and you will see what I mean.