Hi.
When we tried to enable agent autoregistration, everything seemed to go haywire and database queries locked to the moment that the server became unreliable and missed items.
In the server.log we find lots of " became not supported: ZBX_NOTSUPPORTED" for items on the autoregistered hosts and after that:

10123:20120529:121131.604 [Z3005] query failed: [1213] Deadlock found when trying to get lock; try restarting transaction [update ids set nextid=nextid+3 where nodeid=0 and table_name='functions' and field_name='functionid']
zabbix_server [10123]: ERROR file:db.c,line:1412 Something impossible has just happened.

MySQL query graph attached.