Help - I don't think I'm doing anything wrong here. So what's the problem?

Help - I don't think I'm doing anything wrong here. So what's the problem?

I keep getting this error:
1 . [t_695252000000024060] Exception occured while setting value in PreparedStatement for the Column [Successor__695252000000054001] Check whether the datatype for this column is given as specified in the data-dictionary .[t_695252000000024060] Exception occured while setting value in PreparedStatement for the Column [Successor__695252000000054001] Check whether the datatype for this column is given as specified in the data-dictionary 

What am I doing wrong? I have a "single line" field called Successor Activity. Whether I enter something into this field or not, I encounter the message above. 

Help!