Import YouTube Videos (.flv) - 1 works/1 does not

Question

I was wondering if anyone might be able help me with a curious problem in Premiere Pro CS4 (running on Vista Home Basic).
A client came to me to re-edit and update some old marketing videos they had previously uploaded to youtube. They did not have the source files anymore so I had to work off the youtube flash versions. So I played them in youtube and then copied the .flv files out of my internet cache into my project source folder. When I then tried to import both .flv files into Premiere Pro CS4, one of them imported fine, but the other came up with "The file appears to have no media data" error message, and would not import. Both .flv files play fine in the Adobe Media Player. The same problem occured in After Effects CS4 as only one of the two files would import.
The client's files were quite long but I did find some shorter files that also re-created the problem:
http://www.youtube.com/watch?v=T6oIwFGy9JI (4:06)
http://www.youtube.com/watch?v=M8ZfZ5eyeIA (3:45)
Both are versions of the same retro music clip. Curiously it is the one that was more recently uploaded to youtube that imports fine. If you allow both videos to fully buffer you will then will be able to copy them out of your internet cache. If you sort by file size the youtube videos should be near the top with a filename something like; "videoplayback?id=4b0...". When you then copy the files somewhere else they will be renamed something like "video[1].flv". Then if you try importing them into Premiere one will work and one will not and come up with the "The file appears to have no media data" error.
I assume that flash videos can use different video codecs but the generic error message puts a stop to my troubleshooting so I was wondering if anyone with more expertise might be able to shed some light on some possible causes of the problem. The fact that I can't get past is that "Adobe Media Player" can play all .flv files fine so why isn't Premiere Pro capable of just using the same codec?
Thankyou for your consideration,
Chris

Answer 1

Thanks Charles (& Charles).
All of your suggested workarounds worked great. I think what worked best for me was adding the "&fmt=18" to the end of the YouTube URL, which plays a .mp4 version of the video instead, and then after copying out of the interent cache and renaming, Premiere imports the video fine no problems.
That site: http://keepvid.com works great if you don't want to clear your internet cache (as finding specific videos can be a little difficult) although you would be effectively downloading the same file twice, once to view it, another to download.
If as you say the file was originally uploaded as a .flv file then those free converters do a great job at converting them to mpeg2's or other formats.
As it turned out, in testing the "Any Video Converter (Free Version)" I think I found the source of the original problem. When I added both of those aforementioned test .flv youtube videos, the "format" column identified the video that did import onto Premiere as "FLV1" format, and the other which did not as "H264". I then tested this with a few other youtube videos and sure enough all of the FLV1s format videos did import into Premiere but all of the H264 .flv videos would not. They all came up with the "The file appears to have no media data" error message.
So for future forum reference the simple definition of the problem appears to be that Premiere Pro CS4 (and After Effects CS4) will not import a flash video (.flv) that uses the H264 format.
Thanks again Charles(s) for all of your suggestions,
Chris
p.s. During my testing I also tried copying a YouTube HD video (1280x720 .mp4 - Premiere identified it as a XDCAM-EX Movie) out of my cache after playing, and Premiere accepted it no problems