Anyone know how to fix a fatal PHP error?

It sounds like you need to increase the memory limit, for PHP, in the /etc/php.ini file. Then, restart the Apache web server. There was some discussion of this issue & how to fix it, on the node http://drupal.org/node/207036

Everyone's giving me great advice (both here and at the drupal forum) and I'm trying to follow it all, but nothing's worked quite yet. For instance, is there something I should do after adding that line to the settings.php? 'Cause just refreshing my browser window isn't giving me my admin tools back. I've also deleted as many extraneous modules as I could afford, and I've sent an email to the shared webhost requesting a reboot, but they haven't responded yet.

I don't know if you have access to phpmyadmin from your shared hosting but you want to look for a table called cache_menu and clear it out - then try loading the page again. Hopefully that will help.

Otherwise, come on http://webchat.freenode.net/?channels=drupal-la and someone there should be able to help.

Took awhile, but I deleted the extraneous modules, changed the mem limit in settings.php and .htaccess, cleared the cache for menu and admin_menu from phpmyadmin. This didn't work, so then I added the modules back, and then flushed all caches from the Advanced Admin Menu drupal icon (left side), and voila! Success!

Thanks for all the help! I'm totally bookmarking that webchat link for future reference.

When a module's folder is merely removed, left behind are database tables, fields, and these lead Drupal core to display strange things. I've found the white screen of admin death is typically a missing , or similar, and that all the raw HTML is present (try the browser's "View Source" menu item), and to move around to fix/invoke admin buttons, one can copy and paste the needed Action= URL into the browser's Address field, and, if any, concatenate needed CGI parameter pairs (?key1=value1&key2=value2), to get key admin features restored, or disabled (like disabling the module whose folder has been remove). Most times, the module's folder must first be restored, as disabling a module invokes functions in the module that disable it, set core database fields the module is disabled, so core Drupal no longer tries to invoke the module's functions, etc.

I hope that suggests the solution for you to use now. Restore the module's folder, clear cache (you might have to use the copy and paste method - even from from a different drupal install to get the needed pathnames for the domain name), now go to Building Site -> Modules -> and disable the module (again you might have to copy and paste from View Source or a different web site to get the right parameter pairs for a GET - it can be done with POST as well, if you use Firefox tools to mess with the returning POST file - it's worked for me), clear cache again, and it might all come back and work fine.

I'm amazed that Drupal takes abuse at this level, and does not set database values that prevent recovery, for me, a full recovery twice now.

The part where you have 'Cannot redeclare theme_popup_element_title() (previously declared in ........' means that the function theme_popup_element_title has been declared in another module that you are using. The '...' doesn't help narrow down the problem. If you have the whole project on your own computer, try to do a search for 'function theme_popup_element_title'. Then we can figure out a better resolution to the problem. Also, if you don't want the cache to be hit and served to you, add the following line to your settings.php file:

This will ensure that the cache will not be served to you and you can get a better idea on resolving this problem.

From the description of the page for the popup filter module, they recommend using the popup module and the filter module within it. So I would recommend getting rid of the popup filter module since that is at the core of this issue, not jquery ui.