It's possible that your bank changed its server software (I think the IBM/Lotus Domino server might use .do). Until someone mentions a workable solution, I suggest mentioning it to your bank to see whether they can solve the problem on their end.

Thanks very much, BUT, no dice. My bank is very cooperative and spent quite a bit of time trying to help me. They have not changed anything at their end. The .do files can be edited to .pdf and displayed without any problem. However, this is a big nuisance. So is switching to Safari. It is definitely a setting in Firefox and I was suspicious that it was because I was using 4.0.1 but it did work fine until a few days ago. I think I must have elected to use OO and now I can't switch back, but, frankly I can't remember what the dialog box said.

I didn't know that Firefox would append new file extensions to a download, but I only have experience with the Windows version.

To switch the program associated with a type of file, the first stop would be:

Edit > Preferences > Applications

In the search box, type pdf and then wait for the list to filter

Then you should be able to change from OpenOffice to Adobe Reader or your preferred PDF program. Does that work?

I found an even easier way. Find any .pdf file in Finder, right click on it > click on Open With > click on Preview This selects Always Open With. Close Preview and open Firefox. It works.

Thanks a lot for the help. I'll save your method "just in case."