You may receive the following message when closing QuickBooks or performing other functions in QuickBooks Desktop:
The company file cannot be closed at this time because there is another application (Payroll QBCOM Adapter) which is using it.
Payroll Setup (aka UPS) is a component of QuickBooks Desktop that implements the following features: Payroll Setup, Payroll Checkup, EZ-Payroll Item Setup, Edit Filing Methods, Edit Payment Due Dates/Methods. The Payroll Setup component communicates with the rest of QuickBooks Desktop using COM technology.
When Payroll Setup opens, it registers itself with QuickBooks and attaches to QuickBook's COM interface as a client. As it's doing that, it identifies itself to QuickBooks as the Payroll QBCOM Adapter. From that point forward QuickBooks Desktop knows something called the Payroll QBCOM Adapter is hooked up to it, and it expects that client to later properly detach itself again.
If the client fails to detach properly, QuickBooks Desktop will not allow the file to be closed. Therefore, subsequent attempts to do actions in QuickBooks Desktop that require closing the company file will fail with different symptoms, one of them is this error message.
Even if the user closed the QuickBooks Desktop application, its operating system process (called qbw32.exe) still lingers and holds on to the company file. If the user reopened QuickBooks Desktop again, you actually have two running QuickBooks Desktop processes talking to the same company file.
Under certain circumstances Payroll Setup doesn't properly detaches from the QuickBooks COM interface. This is the cause of the error message. Unfortunately, it is not exactly clear why and how it actually fails to do that.
To resolve the immediate problem, see Using the Windows Task Manager utility to end an unresponsive program. After exiting, reboot your computer to ensure that no duplicate processes are still running. You should then be able to load QuickBooks without further problems.
We recommend you to ensure that your QuickBooks Desktop and Payroll are up to date to be able to receive the fix when it is available.