Interbase table with blob (memo) field blues

I have recently re-installed Delphi 3 Client/server with SQL-links and
Interbase 5.5. I have also upgraded my BDE to 5.1.1.

I now have a problem with reading a Blob (Memo) field from an
Interbase table. This field contains data saved as a string, but some
of the characters in this string are full 8-bit characters (i.e. the
most significant bit is set to one). It is these characters that are
now read back incorrectly (e.g. character with ASCII value $A0 will be
read back as $E1). With my previous installation it worked fine.

Does anyone have any suggestions what I might do to rectify this
problem?
--
Pierr van Wyngaard