Strange error in SQL statement

[Sathyaish]

I have a Memo type field in MS Access which is represented in the front end by a Multiline textbox of max length 4000. When I save a new record with 4000 chars in this field, I do not get any error. It works fine. However, when I write an update query for this field with the same data, I get an error saying:

Run-time error '-2147467259 (80004005)':

Could not save; currently locked by another user.

Please see picture attached.

I get this error in the line I execute the SQL statement. If I enter data less than 4000, which is the max length of the textbox I get no error. I also get no error when I add a new record with 4000 chars. If I update a record with data less than 4000 chars for this field, I get no error.

Anyone faced this problem? Please help me.