I am in the same boat. I am looking at a D5 app for a client migrating to D2010. There seem to be 2 problems. One is opening a TIBDataset returning no rows with a blob field and the one you describe below is the other.
AFAICS it doesn't know how to interpret the data, so you need to give the DB a connection a character set.
For your answer see:
Or double click the Database Component and select a Character Set, e.g. UTF8. Now Unicode is still a bit of a mystery to me, so which Character Set to use when your DB isn't set to have one, I don't know.