QuickBooks V2006 is pretty old now and out of support, especially on Vista or newer. You can try a couple of things:
1. See if there is a qbemail.pdf file in the QB program folder. If so, rename it to qbemail.old and try emailing again.
2. Again in the program folder for QuickBooks, there is a file called reboot.bat. Find that. Then open a command prompt, navigate to the folder you just found and run reboot.bat. That does a repair on QuickBooks.
Also, consider upgrading QuickBooks. .... Thinkpads_User