Zero-length character breaking query?

G'day,

I believe I've got some bad data in a table, but I'm not sure how it got there, or how this scenario is possible.

The table is called tdt_unsent.  The field is str_name_l.  For demonstration purposes,  the value is "SMITH".

"select * from tdt_unsent where str_name_l = 'SMITH'" returns 0 rows.
"select * from tdt_unsent where str_name_l ~ '^SMITH'" returns 3 rows.
"select * from tdt_unsent where str_name_l ~ '^SMITH$'" returns 0 rows.
"select length(str_name_l) from tdt_unsent where str_name_l ~ '^SMITH'" returns "5".

So, it's as if there is a zero-length character at the end of the value that is preventing a match.  Is this possible?
Ifso, how could this data have been created? 

Thanks,

Doug Gorley
dgorley@aihs.ca