In access when I click the X, Access does not close

In access when I click the X, Access does not close

If I open a database then click the X the data base closes but not access.

The second time I open the data base I get the error “Database engine cannot lock table.

The only way to close access is to end tasks in the task manager

Then I must delete the locked flies before re opening.

And I can only open it once before re-doing the same process??