Start by checking the permissions on the file and folder as Dave mentions - if the user the software is running under doesn't have read and write access, nor does the application.
If that all looks good, then check the rest of your code: does any part of it create a connection object and forget to close the connection (for best practice, you should use a
block with each creation, so they are automatically closed and disposed when you are finished with them:
using (OleDbCommand Ecom = new OleDbCommand(Query, Econ))
If any part of your software fails to close the connection, no other part of it will be able to open it again until you app closes (or the GC is kicked into life to dispose the redundant object).