Using Windows Vista, Firefox 4.0 and Thunderbird 3.1.9 crash whenever I try to open a file I have downloaded. For Firefox this occurs whether I choose to Open or Save the file and then open it, whenever prompted to download something. In order to access a file I have to save it, close the dialog box, and search for it manually in my Downloads folder. It's the same with Thunderbird, I click on an attachment and am prompted to Open or Save a file. If I click Open Thunderbird crashes immediately, and if I click on Save the file and then try and open the file within the "Saved file" window it crashes. I have to go into Downloads in windows explorer and open it manually. After the crash, I get the message: "C:\Users\Alistair\AppData\Local\Temp\Myfile.doc could not be downloaded because you cannot change the contents of this folder. Change the properties of this folder and try again, or try and save the document elsewhere." This is not the case with either of the other browsers I use (Chrome and IE). If anyone could help me out I'd be extremely grateful, this is driving me absolutely crazy at work! P.S: The window titles and error messages have been translated from french, and my troubleshooting info is in french too, so it perhaps won't correspond exactly to the error message you'd get if you had this problem with firefox in English. Sorry!