Windows 2000 SP2, Server Version: WI-V6.2.794 Firebird 1.0.

Hi, I've a query that, if I add a further join, make my program (or IB_SQL. Or QuickDesk) loose connection with the database!

Here is the query:
SELECT UNITA_U_CLIENTI.ESERCIZIO_ID,
CONDOMINI.CONDOMINIO_ID,
CONDOMINI.NOME COND_NOME,
AMMINISTRATORI.DESCRIZIONE1 AMM_DESCRIZIONE1,
AMMINISTRATORI.DESCRIZIONE2 AMM_DESCRIZIONE2,
AMMINISTRATORI.VIA AMM_VIA,
AMMINISTRATORI.CAP AMM_CAP,
AMMINISTRATORI.COMUNE AMM_COMUNE,
AMMINISTRATORI.PROVINCIA AMM_PROVINCIA,
AMMINISTRATORI.TELEFONO AMM_TELEFONO,
AMMINISTRATORI.PORTATILE AMM_PORTATILE,
AMMINISTRATORI.EMAIL AMM_EMAIL,
AMMINISTRATORI.HOME_PAGE AMM_HOME_PAGE
FROM WK_SELEZIONI
LEFT JOIN CONDOMINI ON (CONDOMINI.CONDOMINIO_ID=WK_SELEZIONI.CONDOMINIO_ID)
LEFT JOIN AMMINISTRATORI ON (CONDOMINI.AMMINISTRATORE_ID = AMMINISTRATORI.AMMINISTRATORE_ID)
INNER JOIN UNITA_IMMOBILIARI ON (UNITA_IMMOBILIARI.CONDOMINIO_ID = WK_SELEZIONI.CONDOMINIO_ID)
INNER JOIN UNITA_U_CLIENTI ON (UNITA_U_CLIENTI.UNITAIMM_ID = UNITA_IMMOBILIARI.UNITAIMM_ID)
INNER JOIN UICC_INFORMATI ON (UICC_INFORMATI.UICC_ID=UNITA_U_CLIENTI.UICC_ID)

This works, but if I add at the bottom:
INNER JOIN CLIENTI ON (UICC_INFORMATI.CLIENTE_ID=CLIENTI.CLIENTE_ID)

Then the connection is lost. Is it a known issue? Where to submit this? What about attaching my database? Help me fix this or make a good bug report, please.
Regards
Marco Menardi