When trying to interface QuickBooks with a 3rd party program, such as EasyAcct, you may receive an error message: "A modal dialog box is showing in the QuickBooks user interface. Your application cannot access QuickBooks until the user dismisses the dialog box."
You may have a window open in QuickBooks that is waiting for a response. This could be a password prompt, another user may be editing preferences, a report may be prompting to memorize, etc.
To resolve this issue, return to QuickBooks and close any dialog boxes. If you do not see any open dialog boxes, then close out of all your running programs (QuickBooks, 3rd party programs, Internet, etc.) and try again. If that does not work, then try rebooting your computer.