"The width of a Unicode text column must be an even number of bytes."

Just received the above error message in Access 2010 when clicking on a checkbox. There's a description of the error here,  which conveniently says

If this error message appears during normal run time, it is probable that the database has become corrupted and needs to be compacted or repaired.

Yup. It's a corruption issue. But compacting and repairing the back-end database did no good. The corruption was apparently in the front-end database file. After I compacted and repaired the front-end, the problem went away.