SQL : ROUTINE ERROR when inserting from another table

Following the documentation to insert into tableA from tableB in the SQL query box from the Management Portal :

INSERT INTO tableA (col1, col2)
SELECT col1, col2
FROM tableB

This straightforward query raises the following error :

Error #5475: routine compilation error : %sqlcq.TESTuNAMESPACE.cls305. Errors: %sqlcq.TESTuNAMESPACE.cls305.cls
ERROR: %sqlcq.TESTuNAMESPACE.csl305.1(14) :
<UNDEFINED>parseExtFrom+19^%qaqcmx
*mt("f", "1^TABLEA") :

Could someone help me decipher this error message ?
Thanks for your help.