Follow the below procedure
In ucweb, Go to www.youtube.com
search the video you want to download and click on it.
On the next page, ucweb wont be able to play video because of the absence of flash player
. No problem! Just go to menu->tools->copy and select 'Page URL'. Now go to menu->tools-> clipboard and press centre button on first link in the list.and then copy it by pressing star key on already selected text of link and then copy.
Now open new window (menu->window->new window) and go to www.keepvid.com
paste it in the URL box on the site(by pressing star key after selecting URL box). Now hit download button next to it. You will get two download links for low and high quality video files. Just click on any link as per your preference and download begins. You can play this flv or mp4 video on your cell with coreplayer 1.3 or higher.
Note: if keepvid.com is unable to give you links to download, just refresh the page(star key by default). Keep refreshing the page till you get download links. Most probably It will not take more than one or two attempts.