I got it to work by changing the FieldKind property on both the blobs to fkInternalCalc. I noticed this requirement on page 89 of the user manual. Weird that I don't have to change it on the non-blob fields and it worked fine in the old version without changing anything.
After upgrading to version 4.05 from 3.4.6, I now get an error when attempting to insert a record into a dataset that includes joined blob fields in the sql query. Inspecting the SQL that's being generated via Oracle Monitor, the insert statement includes these blob fields. Other joined fields...