Sharepoint Business Data List Behavior

This is a multi faceted question, but any help is appreciated

Background:

1. I have a Application Definition with 6 entities using SSO
2. The database back end is Firebird through ODBC
3. All the data is coming from stored procedures

Questions:

1 While trying to implement one or any of the entities from the BDC in a Business Data List web part I get the following error: "An error occurred while retrieving data from . Administrators, see the server log for more inform开发者_开发百科ation." It only happens when I have fields that are null, in this instance a field that was declared as a string.

2.When I check the logs, it's a System.OverFlowException.

3.If I change it so the output from the procedure is a blank string, I suddenly get "The title property of entity is set to an invalid value"

4.The error from the logs after changing to a blank string is "Exception handed to HandleXslException.HandleException System.ArgumentException: '.', hexadecimal value 0x00, is an invalid character" What gives? It worked last night without issue until a record appeared that had a null value in one of the string field. Now, even replacing the null value with something generic is still giving me the title property invalid error.

Most puzzling: If I change the query so that the rows with what would be a null or blank string aren't in the query, the error goes away. But, if I add them back and replace the null string with anything, the error comes back. What the !@#$? How does it know I've replaced a null value with something else before the records are returned to the XmlReader?

I've run into this exact scenario and it brought back some angry/confused moments. As you said in your comment:

I set the encoding to be unicode on all varchar and char outputs and it fixed it. The lack of encoding caused there to be null characters (not a null record, but one null character) for that column and Sharepoint could not parse the field. Changed the encoding, and everything works.

It took me a couple days of swearing at the computer before we took it down to the metal and discovered the unicode issue. I don't even know when it changed but we realized the same thing and all was right with the world again.