> SQL> DECLARE EXTERNAL FUNCTION GUID_OCTETS
> CON> RETURNS CHAR(16) CHARACTER SET OCTETS FREE_IT
> CON> ENTRY_POINT 'GenGUID'
> CON> MODULE_NAME 'BinGUID.dll';

Beware! Returning CHARs and VARCHARs from UDF is broken !
The only type that works is CSTRING.
(I have not tried fb1.5.2, but it is not mentioned as fixed in release notes)

Ivan