After upgrading to new 2.0.5 version we have:
6700:20130222:031443.782 [Z3005] query failed: [-1] ORA-00060: deadlock detected while waiting for resource
6218:20130222:031448.614 [Z3005] query failed: [-1] ORA-00060: deadlock detected while waiting for resource
6918:20130222:031451.613 [Z3005] query failed: [-1] ORA-00060: deadlock detected while waiting for resource
6122:20130222:031455.817 [Z3005] query failed: [-1] ORA-00060: deadlock detected while waiting for resource
6671:20130222:031531.993 [Z3005] query failed: [-1] ORA-00060: deadlock detected while waiting for resource
7423:20130222:031535.581 [Z3005] query failed: [-1] ORA-00060: deadlock detected while waiting for resource

which causes to grow usage of cache write buffer and eventually to crash zabbix_server after a while (1-4h).
I made many tests and it remains the same. When I run environment with zabbix_server 2.0.4 it is OK, but with 2.0.5 - it dies.

Fix
ZBX-5920 added prefetching of 2 MB of data for Oracle SQL selects
seems to work, but I think in this fix is modification which causes above errors.