Well, I seem to be in a pickle (big surprise, eh?).

I took Laurie to the airshow yesterday. We both had our cameras, both of which have video capability. Between the two cameras, I have a good 100 pictures and about 40 videos. So I plug in her camera and download all the pics and videos. Because I don't have my patch cord here, I was going to download my pics and videos from my camera when I get back to AZ.

I created a new sub album in my PhotoBucket account, but when I try and download the video it says "invalid file extension." I tried to change that, but it won't change except in title - the file TYPE won't change, in other words.

The files on her camera only say (for example) "MVI_660" That's it - no [dot] dv or anything. And no matter what I try, PB will not allow me to upload the videos. Pictures, yes. But not the videos.

So, umm, what do I do to correct this? Do I need a hosting site that recognizes the "MVI_" as a valid file extension, or is there some way to change the extension (even though there doesn't seem to even be one)?

I have some kick ASS video of the US Air Force Thunderbirds (and many others) that I'd like to share with the various forums I visit, but I can't get the damn things to download to my PB account.

Any suggestions/help? Please?

Why don't you right click on the video file and then on the menu that pops up, select properties.
Then it'll tell you what the format is.
Photobucket may have an issue with the format. The next step is to go to a search engine and look for a video format converter OR, you can attempt to use Windows Movie Maker which is included with your computer if you have Windows.
If you have Movie Maker, you can try clicking and dragging the video onto the project window of the program. Drag the icon down onto the bit that looks like a movie film strip. Go to the FILE menu and there should be something like "save movie" or something like that... shortcut will be CTRL+P.
Then your video will be saved as a .wmv file which is compatible with Photobucket.
If this doesn't work, then download a converter. Type in the format name of your file and that of a more standardized format (like .avi or .wmv or .mpeg) and the word "converter." You should find something.
I guess what comes after that is fairly self expanitory. Download, install, run and convert.