Checking the log-file give:
action:

and error:

Query: DELETE FROM cscart_bm_snapping WHERE object_type='categories' AND FIND_IN_SET(228, object_ids)
Backtrace››
/home/boranweb/public_html/core/fn.database.php (db_error): 268
/home/boranweb/public_html/core/classes/bm/block.php (db_query): 752
/home/boranweb/public_html/core/fn.catalog.php (remove_dynamic_object_data): 1532
/home/boranweb/public_html/controllers/admin/categories.php (fn_delete_category): 123
/home/boranweb/public_html/core/fn.control.php (include): 617
/home/boranweb/public_html/core/fn.control.php (fn_run_controller): 441
/home/boranweb/public_html/admin341.php (fn_dispatch): 24
What to do?
Version 3.01