Martha Van Burek:
Thank you for your post, and I apologize for the late reply.
Something has changed with your file. If you hold down the option key when accessing the file, are you able to get a prompt for the user name and password? If so, try entering a full access username and password. If this fails, then you'll need to revert to your last Backup file.
I know it has been more than two months since your reported this, so if you have found a resolution, please post here so others who encounter the same symptom can benefit. If you are still having difficulty, please let me know.