For everyone using Leopard or beyond trying to follow "surfinsd" instructions:
1) The target directory is one of those contained in /private/var/folders, and you have to find which one belongs to YOU. To accomplish that, start playing a video in your browser (Safari, Firefox, etc). While it is playing, "pause" it.
2) From Terminal.app, issue the following command:
ls -lR /private/var/folders >$HOME/Desktop/myvar.trace.txt
This will overwrite any existing "myvar.trace.txt" on your Desktop.
3) cat $HOME/Desktop/myvar.trace.txt | grep Flash
If that command shows a FlashTmp file, then you can find your target folder.
4) cd $HOME/Desktop
vi myvar.trace.txt
Use the Visual Editor (vi) to examine this file created by ls -lR
Use "/Flash" (without the quotes) to find a line with Flash in it.
Somewhere above you'll see a "./two-character-folder-name followed by a / and much longer name that starts with those same two characters and ends in some UPPER CASE two characters followed by another / and folder name.
For example: ./ta/taQuant-G6vxRupeR30+++TI/-Tmp-
Whatever it is, that's the folder trio receiving your video file. Make a note of the front and back: /ta/ta*TI/-Tmp-
I used an asterisk as a universal match because you'll use it with the real video you want to capture. You only need to determine this path once for YOURSELF. Other accounts on your Mac will have different paths.
:q! [to quit from the Visual Editor]
You can now safely trash the "myvar.trace.txt" file.
5) cd /private/var/folders/ta/ta*TI/-Tmp-
This should take you to the place where your flash videos are stored. But they can disappear as soon as they are finished being shown. That's why you "pause" the video in your browser, to hold onto it temporarily.
6) ls -l Flash*
Do this while positioned in your flash folder. Make a note of the full name of the file. You should see the size increase as more and more is downloaded, even if you have the video paused. Once the download completes, the size will remain static. Once that happens....
7) cp FlashTmp.suffix $HOME/Desktop/pick-any-name.flv
"suffix" is the appendage on the FlashTmp file that was downloaded.
Pick a name for your final file, and use the ".flv" suffix to identify it.
You can now release your "pause" on the video and stop it.
Caution: Sometimes multiple videos are downloaded at the same time, from different windows in your browser. Be sure you have just one window.