Featured Images not getting attached to posts

Hi,

I am not being able to attach featured image to my posts. It was working fine till now. But yesterday I used the Next-Gen Gallery plugin. And after that when I click on the “Set Featured Image” button, it just says saving, but never actually saves it. I can upload pictures. I did try de-activating all plugins as well. But its not working.

I don’t know if this piece of code in singlepost.php is of any help in analyzing the problem. But here it is:

<div id="omc-inner-placeholder">

				<?php if($category[0]){ echo '<a href="'.get_category_link($category[0]->term_id ).'" class="omc-flex-category">'.$category[0]->cat_name.'</a>';} ?>
				<?php if (has_post_thumbnail()) { ?>

					<?php the_post_thumbnail('featured-image', array('class' => 'featured-full-width-top')); ?>

				<?php } else { 

					echo('<img src="'.get_template_directory_uri().'/images/no-image-featured-image.png" class="omc-image-resize" alt="no image" />');

				} ?>

I am not very experienced so I really hope you will be able to help me.