Opening Simply Accounting error messages

Hi,

My Simply accounting program has been working fine until I tried opening it today and got an error message:

"Simply Accounting cannot open the database because some database files are read-only. Please ensure you have sufficient rights to the files, then try again."

and

"Cannot understand the date. Be sure you have entered the date in a standard format and verify that it is a valid calendar date."

I have not changed anything since the last time I worked in my files. Can you help?

Thank you.