I get this error when I click on one of my categories and I don't know how to fix???????
Fatal error: Call to undefined function the_post_thumbnail() in /home/content/t/r/i/tricky99/html/blog/wp-content/themes/atahualpa/functions/bfa_post_parts.php on line 124

Can someone tell me how to fix????????

M guess is that you are on WP 2.8.x and uploaded Atahualpa 3.4.5 - this version had a bug in it, it called the function with out checking if it existed. There is a new version of Atahualpa 3.4.5.1 you need to install from http://wordpress.bytesforall.com/?p=82

That is exactly what I did....If I download the new version, will I loose all the changes and settings I did?

No, the settings are stored in the DB - there is an outstanding issue with thumbnails, so don't use them for the moment

Thank you for all your help.... I downloaded the fix and I have it on my desk top so how to I install this from there? I can't seem to find instructions on the forum.

Unzip the download ( you should get a folder called atahualpa345) and FTP the result to the wordpress/wp-content/themes folder then go into the dashboard->appearances-Themes and activate the atahualpa theme version 3.4.5.1