Eureka! ok, so I'm posting what I've found just in case someone else runs into this problem...
Turns out that one of the mysql tables were corrupted, I found this out while trying to do a mysqldump to copy the table so I could test a later release...
mysqldump: Can't get CREATE TABLE for table `mdl_quiz_states` (Can't open file: 'mdl_quiz_states.MYI'. (errno: 145))
and so I performed the following command in mysql console...
mysql> CHECK TABLE mdl_quiz_states FAST QUICK;
+------------------------+-------+----------+-------------------------------------------------------+
| Table | Op | Msg_type | Msg_text |
+------------------------+-------+----------+-------------------------------------------------------+
| moodle.mdl_quiz_states | check | warning | Table is marked as crashed |
| moodle.mdl_quiz_states | check | warning | 1 client is using or hasn't closed the table properly |
| moodle.mdl_quiz_states | check | error | Can't read key from filepos: 742400 |
| moodle.mdl_quiz_states | check | error | Corrupt |
+------------------------+-------+----------+-------------------------------------------------------+
4 rows in set (0.03 sec)
and I applied the REPAIR TABLE command on that table....
mysql> REPAIR TABLE mdl_quiz_states;
+------------------------+--------+----------+------------------------------------------------------------------------------+
| Table | Op | Msg_type | Msg_text |
+------------------------+--------+----------+------------------------------------------------------------------------------+
| moodle.mdl_quiz_states | repair | info | Key 1 - Found wrong stored record at 1034212 |
| moodle.mdl_quiz_states | repair | info | Key 1 - Found wrong stored record at 1099756 |
| moodle.mdl_quiz_states | repair | info | Key 1 - Found wrong stored record at 1102828 |
| moodle.mdl_quiz_states | repair | info | Found link that points at 7277817043133631284 (outside data file) at 1102944 |
| moodle.mdl_quiz_states | repair | info | Found link that points at 7638105010102050544 (outside data file) at 1103016 |
| moodle.mdl_quiz_states | repair | info | Found link that points at 288230426823335807 (outside data file) at 1103040 |
| moodle.mdl_quiz_states | repair | info | Found block with too small length at 1103352; Skipped |
| moodle.mdl_quiz_states | repair | info | Found block with too small length at 1103360; Skipped |
| moodle.mdl_quiz_states | repair | info | Found block with too small length at 1103448; Skipped |
| moodle.mdl_quiz_states | repair | info | Found block with too small length at 1103520; Skipped |
| moodle.mdl_quiz_states | repair | info | Found block with too small length at 1103528; Skipped |
| moodle.mdl_quiz_states | repair | warning | Number of rows changed from 42801 to 42716 |
| moodle.mdl_quiz_states | repair | status | OK |
+------------------------+--------+----------+------------------------------------------------------------------------------+
13 rows in set (0.98 sec)
mysql> CHECK TABLE mdl_quiz_states FAST QUICK;
+------------------------+-------+----------+-----------------------------+
| Table | Op | Msg_type | Msg_text |
+------------------------+-------+----------+-----------------------------+
| moodle.mdl_quiz_states | check | status | Table is already up to date |
+------------------------+-------+----------+-----------------------------+
1 row in set (0.00 sec)
now everything is back to normal...