You're probably auto-including a file from two different files in different levels of directories:
mosaic/include/alpha.php mosaic/whatever mosaic/ajax/file.php
The "../../" specification works from a file in "mosaic", but not from a file in any directory under it. Either use absolute file specifications (e.g. '/var/www/site/htdocs/mosaic/include') or fix your include_path and just use 'alpha.php' in your includes.