I have this problem. I made a SQL method for storing strings into an Interbase field. If I insert a string containing a stressed wovels (like " è ") directly into the DB it works, but if I use my SQL method it gives me this error:

*Error, /Products.gvibDA.gvib.gvibExceptions.DataError/:* - arithmetic exception, numeric overflow, or string truncation -- Cannot transliterate character between character sets

What is the matter? Is it a GV Interbase adapter's bug?

I nerver seen the GV Interbase adapter, but this error message clearly indicates that you missed lc_ctype=your_encoding parameter when connecting to interbase server. Try to look at adapter's docs (or sources) or ask its developers