This error is definitely because you modified the definition of this column in the table.

The client program is supposed to fetch this column into a varchar2 variable with the same length, then you increased the column in database, which exceeds the length of the client variable, now the client program has to truncate the value fetched from database to fit into the variable.

This is the very scenario where anchored variable is useful.

http://www.itpub.net/showthread.php?threadid=195180&pagenumber=