cannot see thumbnails in edit, even though they exist on server

hello my friends
I know this wordpress I use is pretty old, but even the new version doesn’t solve the problem.
here is the case.
I have a wordpress installation where I have about 1000 posts, pages in common. Everything works fine until about 2 weeks ago, for some reason all pictures I have uploaded seams like the don’t have thumbnails. But they are on the server still and even the sql has some lines with their name all seams to be normal.
I tried to post new image and whoala it doe’s have the thumbnail, but not the old ones. I even compared lines of the old and new _wp_attachment_metadata in sql and it seams normal as far as I can tell.

here is short code of the sql output: two last lines includes working image.

(1956, 1009, '_wp_attachment_metadata', 'a:0:{}'),
(1958, 1011, '_wp_attachment_metadata', 'a:0:{}'),
(1959, 1010, '_wp_page_template', 'default'),
(1963, 1013, '_wp_attachment_metadata', 'a:5:{s:5:"width";i:350;s:6:"height";i:245;s:14:"hwstring_small";s:23:"height=''89'' width=''128''";s:4:"file";s:81:"/www/doc/www.revolta.cz/www/wp-content/uploads/2008/06/svaly-pozvanka.png";s:5:"thumb";s:28:"svaly-pozvanka.thumbnail.png";}'),
(1965, 1014, '_wp_attachment_metadata', 'a:5:{s:5:"width";i:350;s:6:"height";i:262;s:14:"hwstring_small";s:23:"height=''95'' width=''128''";s:4:"file";s:85:"/www/doc/www.revolta.cz/www/wp-content/uploads/2008/06/nike-sparta-18_upr.jpg";s:5:"thumb";s:32:"nike-sparta-18_upr.thumbnail.jpg";}'),
(1966, 1015, '_wp_attached_file', '/www/doc/www.revolta.cz/www/wp-content/uploads/2008/06/nike-sparta-28_upr.jpg'),
(1967, 1015, '_wp_attachment_metadata', 'a:5:{s:5:"width";i:350;s:6:"height";i:262;s:14:"hwstring_small";s:23:"height=''95'' width=''128''";s:4:"file";s:85:"/www/doc/www.revolta.cz/www/wp-content/uploads/2008/06/nike-sparta-28_upr.jpg";s:5:"thumb";s:32:"nike-sparta-28_upr.thumbnail.jpg";}'),
(1969, 1016, '_wp_attachment_metadata', 'a:5:{s:5:"width";i:348;s:6:"height";i:332;s:14:"hwstring_small";s:23:"height=''96'' width=''100''";s:4:"file";s:84:"/www/doc/www.revolta.cz/www/wp-content/uploads/2008/06/promo-set-siemens.png";s:5:"thumb";s:31:"promo-set-siemens.thumbnail.png";}'),
(1970, 1017, '_wp_attached_file', '/www/doc/www.revolta.cz/www/wp-content/uploads/2008/06/centrum-cz-ajznbonak.mp3'),
(1971, 1017, '_wp_attachment_metadata', 'a:0:{}'),
(1972, 1018, '_wp_attached_file', '/www/doc/www.revolta.cz/www/wp-content/uploads/2008/06/centrum-cz-moskyti.mp3'),
(1973, 1018, '_wp_attachment_metadata', 'a:0:{}'),
(1974, 1019, '_wp_attached_file', '/www/doc/www.revolta.cz/www/wp-content/uploads/2008/07/dsc_2693.JPG'),
(1975, 1019, '_wp_attachment_metadata', 'a:5:{s:5:"width";i:350;s:6:"height";i:232;s:14:"hwstring_small";s:23:"height=''84'' width=''128''";s:4:"file";s:67:"/www/doc/www.revolta.cz/www/wp-content/uploads/2008/07/dsc_2693.JPG";s:5:"thumb";s:22:"dsc_2693.thumbnail.JPG";}');

Do you know what’s the matter?

thx