0x80040404 - indicates that the version of QuickBooks currently running does not support 3rd party applications connecting to it
0x80040409 - indicates that the version of QuickBooks currently running cannot work with the provided data file
0x8004040A - indicates that the data file already open is different from the requested one.
0x80040154 & 0x800401f3- indicates a permission error to access QuickBooks via an application
0x8004041c & 0x800401f3 - If you are running 64bit windows then please try with UAC switched off.
If you are using Microsoft Vista or 7, please ensure that you have User Account Control (UAC) set to On or Always Notify. (if changing UAC you will need to reboot Windows for the change to take affect). However if you are using a 64bit version of Windows and you receive an unable to connect message you should turn UAC off, reboot and then try a connection.
Send us a file called qbsdklog.txt on Vista and Windows 7 it should be located in C:\ProgramData\Intuit\QuickBooks , on XP you will find it in this folder C:\Program Files\Common Files\Intuit\QuickBooks