The usual reason for this is that the server is sending a generic binary content type header with the file rather than a specific one. Firefox relies on that header to match up a download with its handler; it doesn't use the file extension.

You can see the headers if you use an add-on like Firebug or an external proxy like Fiddler2. (But I don't know whether that additional level of research is justified... if you confirm that it's a generic content type, you would need to get your financial institution to fix its server software.)

There might be an add-on to solve this problem, but based on a quick search, I don't have a specific recommendation.

Thanks for the answer. I'm guessing you're correct about the generic header, but it occurs with every financial institution I use, and Safari has no problems with any of them. I guess Safari might be using the extension to id the file-opening app, but all of my financial institutions are using generics? Shoot, maybe I need to change banks ;-)

If it affects multiple different FIs, then I wouldn't rule out a problem with Firefox. The problem is that the mimeTypes.rdf file has a messy structure, so I don't recommend editing it manually. Hopefully someone will have an alternative solution.

Just chatted with Firefox... cannot do it as it's content sent along by the financial institution that Firefox must ask if you want to save the file... Oh well.

Firefox is been doing this to me for years for every application, i.e.: Word, Excel, PowerPoint, etc. It is very annoying, mostly this is why I switched to Chrome.