I can't send attachments with Thunderbird. I can write a message but when I click on Attach, I get the message "Thunderbird has stopped working. A problem has caused the program to stop working correctly. Windows will close the program and notify you if a solution is available." There is only a "CLOSE PROGRAM" button displayed and when I click on it Thunderbird stops running. I'm not sure whether this is a Thunderbird problem or a Windows 7 problem. Any ideas on what is causing this and how to fix it?