This week (14 Feb 11)I upgraded to actual release 1.9.10.
I use a lampp environment and also upgraded from lampp1.7.0 to 1.7.4

Afterwards teachers could not see uploaded assignments any more.
When clicking on the assignment, I can see "View 21 uploaded assignments"
When clicking on this link the new page says:"Nothing to display".

I switched on debuggingmessages in Moodle
and got the message:
BIGINT UNSIGNED value is out of range in '(`moodle`.`s`.`timemarked` - `moodle`.`s`.`timemodified`)'

SELECT u.id, u.firstname, u.lastname, u.picture, u.imagealt, s.id AS submissionid, s.grade, s.submissioncomment, s.timemodified, s.timemarked, COALESCE(SIGN(SIGN(s.timemarked) + SIGN(s.timemarked - s.timemodified)), 0) AS status FROM mdl_user u LEFT JOIN mdl_assignment_submissions s ON u.id = s.userid AND s.assignment = 195 WHERE u.id IN (1432,1242,1341,1245,1285,1270,1271,1307,1246,1240,1254,1310,1252,1435,1250,1267,1308,1258,1260,1298,1266,1259,1275,1387,1391,1268,1295) ORDER BY lastname ASC

• line 686 of lib/dmllib.php: call to debugging()
• line 966 of lib/dmllib.php: call to get_recordset_sql()
• line 1186 of mod/assignment/lib.php: call to get_records_sql()
• line 524 of mod/assignment/lib.php: call to assignment_base->display_submissions()
• line 43 of mod/assignment/submissions.php: call to assignment_base->submissions()

Playing a bit with phpMyadmin I got the following values for timemarked and timemodified
timemarked timemodified
0 1297868046
0 1297886884
NULL NULL
0 1297793028
0 1297874405
0 1297882318
0 1297797923
0 1297361972
0 1297788713
0 1297874030
0 1297896379
NULL NULL
NULL NULL
0 1297697608
0 1297701961
0 1297876458
0 1297516949
NULL NULL
0 1297794067
NULL NULL
0 1297868094
0 1297794223
0 1297890846
0 1297705068
0 1297870591
NULL NULL
0 1297873283
*************************************************

I assume that the mysql in lampp1.7.4 is more strict than the mysql in lampp 1.7.0

Proposed solution:
in moodle/mod/assignment/lib.php line 1186
change
//********************** OLD
$select = 'SELECT u.id, u.firstname, u.lastname, u.picture, u.imagealt,
s.id AS submissionid, s.grade, s.submissioncomment,
s.timemodified, s.timemarked,
COALESCE(SIGN(SIGN(s.timemarked) + SIGN(s.timemarked - s.timemodified)), 0) AS status ';
//**********************

to
//********************** NEW
$select = 'SELECT u.id, u.firstname, u.lastname, u.picture, u.imagealt,
s.id AS submissionid, s.grade, s.submissioncomment,
s.timemodified, s.timemarked,
COALESCE(SIGN(SIGN(s.timemarked) + SIGN(CAST(s.timemarked AS SIGNED) - CAST(s.timemodified AS SIGNED))), 0) AS status ';
//**********************

Best regards
Klaus