Solved..
I dug a little deeper and installed GD module for PHP. It worked like a charm!
Look here:
http://wordpress.org/support/topic/149941
http://wordpress.org/support/topic/169157
How to test: create a file, let’s say test.php and write the following inside:
<?php
header (“Content-type: image/jpeg”);
$img = ImageCreate (200,100);
$fond = ImageColorAllocate ($img,0,200,0);
$col = ImageColorAllocate ($img,255,255,255);
ImagePolygon ($img,array(60,10,140,10,190,90,10,90),4,$col);
ImageJPEG ($img, ”, 100);
?>
Save the file, chmod 777 it (just in case), and then point your browser to http://yourdomain/test.php. If a white polygon shows up on a green background, this is not your problem.
it’s called nextgen gallery