Thank you "therube" for replying. Sorry for the late reply.
Regarding the "multiple parts", take this YouTube video for example:
http://www.youtube.com/watch?v=Y5lO4hEAJHU
As soon as the video starts playing, I can left-click the FlashGot icon and the "FlashGot (Browser Built-In)" window pops-up (so, yes, I'm using the built-in download manager, no other add-on/extension) asking me where I'd like to save the ".flv" file. Once I click "Okay", the download I end up with is a 1.48MB file, which plays only the first 22 seconds of the video.
Now, if I wait a while, I can no longer left-click the FlashGot icon, because there are now multiple videos/parts available to download apparently. So, if instead, I right-click the FlashGot icon, and select the first/top available video/part (which it states is a 1MB video), and click "Okay" in the destination selection window; I get the same file as in the paragraph above.
If we take the last paragraph (immediately above) and go a step further, and select the second video/part, click "Okay"; then, I end up with a video that is 1.17MB in size, and 42 seconds. However, there is no audio for the first 22 seconds (I suppose that data is from that first 22 second video), while it displays a still image from somewhere between the 23-42 second marks. This indicates to me that FlashGot was only able to download the "second part" or 23-42 seconds from the original video.
If we try the third video/part, I get a 1.09MB video, that is 1 minute and 2 seconds in length, but where there is no audio for the first 42 seconds.
However, when the same YouTube video (it's links to the same address as above) is linked/played in another website, FlashGot acts normally. See:
http://viralvideochart.unrulymedia.com/ ... 5lO4hEAJHU
At this alternate website, I can left/right-click (as FlashGot only detects one downloadable video), and I end up with a proper (here, assuming you are just viewing the 360p version of the video) full-length 8.6MB (well, FlashGot reports 9MB if you right-click the icon because it's rounding up) video that is 3 minutes and 41 seconds in length.
I hope you can understand my problem now, and hopefully help me find a solution. Thank you!