The cell title field of the matrix is limited two 255 charaters. When a new row or column is added, the cell title is autopopulated with a string that concatenates the values in row label: row name; column label: column name. If the total string length is > 255 characters, a stack trace is generated and the matrix becomes unusable. While there are currently character limits on the column and row label fields (25 chars each), the cell and column name fields allow very long strings (> 400), so there is nothing that prevents users from creating a matrix results in exceeding the 255 character limit.
To fix the problem, we can either set character length restrictions on the row and column name fields (e.g., 100 chars each) or modify the field length of the cell title field to permit longer concatenated strings. We are inclined to move forward with the first option, since it won't require changes to the database, but would like to discuss at the Monday call before proceeding.
One important note. This bug can only be reproduced by creating and saving new row or column that results in exceeding the limit. If you edit an existing row or column name, the stack trace will not occur because, by design, the cell title field is not updated when such changes are made.
To reproduce the error, create a new matrix, add one row and one column, and make tjhe combined length of their names > 255 chars. Then try to open the matrix. You should receive a stack trace.