User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.9.1.8) Gecko/20100225 Firefox/3.5.8 Build Identifier: I run TB in kde4 on FreeBSD. When I double click on the .pps attachment, TB first offers me to use kpresenter. I choose OpenOffice, but the option: "Do this automatically for files like this from now on.: is grayed out. So next time it offers me kpresenter again, and I have to select OpenOffice again. Also screen "Download Actions" (in Preferences) only allows to change DOC, DOCX and RTF file apps. There is no option to add a new type. I think both grayed out option and lack of capability to add new file extension are problems and should be fixed. Reproducible: Always

What is the mime-type for you file (the file extension doesn't matter) ? It's only greyed out for application/octet-stream.

Content-Type: application/octet-stream Then this is a problem: it should never be grayed out and should be by he extension.

This is the major usability issue. pps files, and some other attachments that pass through application/octet-stream, are very common. And the need to choose the app every time is very annoying.