I just wanted to signal a not so obvious error :
ORA-01891 Datetime/Interval internal error SQLState 22008 ErrorCode 1891
This happens when I try to access a table that is accessible via an Oracle dblink.
The error did not appear when I used plain SQL*Plus ; this has been driving
us mad for a few days.
The error disappears when I uncheck, in the global preferences/Oracle tab,
the "Initialize Session Timezone".
Hope this can help other people not to get stuck.