When Flash 10 first came out, all of Stardock's sites had trouble with it. Most of the problems have been fixed, but I'm not sure if the uploading problem has. I run flash 10 on my 2 main computers, and I have not uploaded from them for months.
Ever since I got Flash 10 (with cs4) on my main computers, my uploads have been done with my older XP machine which still has Flash 8. Flash 9 also works, though.
Hope this helps. 