No Thumb images, rest fine

I got yet an other problem with the thumbnails in BG (using JPGs, didn't check others). Everything worked fine until recently, I am not sure what caused it. I installed a few modules, but I switched back to the old versions on all I could remember. It is always the same. No Thumbnails, but the table is there with links and everything. Full size Images work fine and show as expected with lightbox2.

I did read the other issues (#220430: Yet another "no thumbnails!" issue, #186863: table populated with image tags, but they don't display) and tried most of the proposed solutions. I installed BG 5.x-2.17 and BG 5.x-1.x-dev (2008-Mar-01), both same problem.

Also I tried to find the cause of the problem. The following things I can say for sure (but I am not a PHP or web developer):

• the path to the images seems to be correct. I did print out the path (base64_decode( $_GET['imgp'] )) in images.php and it is valid and correct as far as I can tell.
• I attempted to use db caching and file caching both with the same result. Files are there if file caching is active, I guess db as well but didn't check.
• no software has changed (same PHP, MySQL, Apache) from working version to non-working.
• no error in any log file I checked.
• there should be enough resources free on the system. Webspace as well as memory (also for PHP to use)

A few things (maybe bugs or my lack of knowledge ;)) I found missing:

• missing require_once './includes/file.inc'; for file caching.
• variable_get('brilliant_gallery_cache', 'd') == 'f' seems to be always false (no matter how I change the setting over the UI. I manually enabled file caching removing the IF statement.

I am out of guesses on what could be the reason for this. I have multiple sites with BG and all work fine just the one doesn't work. Any suggestions are very welcome.

some infos on the drupal installation:

• GD library 2.0 or higher
• MySQL database 5.0.27
• PHP 4.4.4-8+etch4
• Web server Apache/2.2.3 (Debian)
• Clean URLs enabled
• Critical modules I could think of: Localizer (used 3.2 & 3.3)

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