BDE 16 and GPE

using SQL-statements like this causes a GPF in the BDE 16 Bit (IDQRY01.DLL).
Inprise Helpline told me that they do have heard about that but theres no
fix. I would like t know the exact reason to avoid GPFs in my application.
Example tested with DBF and Paradox files and all BDE 2.5x Versions uses
TQUERY component:
select * from kd, ld, pat where
(pat.ptnum=ld.ptnum) and
(pat.ptnum=kd.ptnum) and
((:today - pat.gebdat) < 30000)
Removing the parameter :today and using a fixed number does not solve the
problem. Most likely it seems to be a problem using calculation and
comparison in one statement?
Any help or idea is very, very welcome!
Thanks in advance
Michael Schumann  (nospam: swap o and t after @)