Crystal Reports 8.5 - SQL Expressions

Hello,

I'm using Crystal Reports 8.5 against PostgreSQL Database Server 8.1.
The thing is that when I try to use an SQL Expression Field in Crystal,
doesn't work (it does work when I don't use it).

Returns the following error:
Error in compiling SQL Expression:
Cannot find parser table file(s).

The expression is the folowing:
{fn SUBSTRING( TABLE."column", 1, 250 )}

(column datatype is "text")

This sentence worked against other databases, but not against PostgreSQL...

Has anybody pass through this situation?

Thanks for your assistance,

Juan