> I just found out by accident that including the old gds32.dll (dated
> 7/14/2004) in the Windows/System32 folder seems to do the trick.
> Doing the same with fbclient.dll does not work.
>
> Hmmm, do I need to recompile my custom .dll?

Why do you ask ? If they are *your* custom functions, then you must know
what dependencies you created :)
The only reason why udf could be linked to client library
is that it uses isc_encode_sql_date(), isc_decode_sql_date(), ... functions.
Do not know what language you use, but e.g. in Delphi it is trivial
to directly convert between FB types and TDateTime,
without these isc_xxx functions.

Ivan