Regarding Point Number (3). JIC the following Debug log could help evaluate the cause. Basically, It's the same as with many others, where some Links are editedable and the others are not. In this case it is wrt cats and subcats.

Subcats Which Can Be Modified

GT::SQL::Driver::MYSQL::sth (22080): Executing query: SELECT * FROM lsql_Category WHERE ( ID = 47 ) from Links::Browser::category_modify_form at (eval 641) line 12
GT::SQL::Driver::MYSQL::sth (19841): Executing query: SELECT ID,FatherID,Full_Name,Name,Number_of_Links FROM lsql_Category WHERE ID = 47 from Links::Category::_plg_modify at /admin/Links/Category.pm line 180
GT::SQL::Driver::MYSQL::sth (19841): Executing query: SELECT Timestmp FROM lsql_Category WHERE ( ID = 47 AND Timestmp > 20040301015901 ) from Links::Category::_plg_modify at /admin/Links/Category.pm line 201
GT::SQL::Driver::MYSQL::sth (19841): Executing query: UPDATE lsql_Category SET Description = '' , Newest_Link = '0000-00-00' , Category_Template = '' , Meta_Description = '' , Name = 'Driving Schools' , Footer = '' , Header = '' , Has_New_Links = 'No' , Number_of_Links = 0 , Has_Changed_Links = 'No' , Full_Name = 'Automobiles/Driving Schools' , Meta_Keywords = '' , FatherID = 30 WHERE ID = 47 from Links::Category::_plg_modify at /admin/Links/Category.pm line 201
GT::SQL::Driver::MYSQL::sth (19841): Executing query:
SELECT lsql_Links.ID
FROM lsql_CatLinks, lsql_Links
WHERE lsql_CatLinks.LinkID = lsql_Links.ID AND (lsql_CatLinks.CategoryID = '47')
ORDER BY isValidated DESC, Title ASC LIMIT 0, 25
from Links::Browser::_links_list_html at /admin/Links/Browser.pm line 1419

Subcats Which Cannot Modified

GT::SQL::Driver::MYSQL::sth (19842): Executing query: SELECT * FROM lsql_Category WHERE ( ID = 33 ) from Links::Browser::category_modify_form at (eval 641) line 12
GT::SQL::Driver::MYSQL::sth (19842): Query execution took: 0.000941s from Links::Browser::category_modify_form at (eval 641) line 12
GT::SQL::Driver::MYSQL::sth (21673): Executing query: SELECT ID,FatherID,Full_Name,Name,Number_of_Links FROM lsql_Category WHERE ID = 33 from Links::Category::_plg_modify at /admin/Links/Category.pm line 180
GT::SQL::Driver::MYSQL::sth (21673): Executing query: SELECT Timestmp FROM lsql_Category WHERE ( ID = 33 AND Timestmp > 20040226121328 ) from Links::Category::_plg_modify at /admin/Links/Category.pm line 201
GT::SQL::Table (21673): The record you are attempting to modify has changed since you last accessed it. at /admin/Links/Category.pm line 201.
[Mon Mar 1 03:52:12 2004] [error] Invalid Request: '' 'category_modify' at /admin/admin.cgi line 65.

Please note that the full paths have been removed from the above and only /admin onwards are given. There are no Links in the DB.

Any Clue?

Anup