After countless deletes and reloads of both TCPMP 0.72RC1 and the bundled flash cab file as well as one needless hard reset, I FINALLY got full YouTube working on my Samsung I760.
The issue was that PIE simply wasn't responding to Youtube video links as I saw on posted sucessful videos. The submenu to select Play-Save-Linked never showed up and I would get a message that the video "is no longer available and may have been remorved".
After a search and visit to a site call wmexperts.com and this link:
Full Youtube, it now works.
EDIT: I was wrong, you don't need to access the Video Sites shortcut. Full Youtube videos work with direct access to Youtube with PIE.
The "Real Secret" (and quite frankly it may have always been available during one of the many loads of the flashbundle) is that when Youtube is displayed in PIE, to select a video, BRIEFLY tap the video icon to see the "Play-Save-Linked" submenu. If you hold the stylus too long, the submenu is skipped to the default PIE submenu. (See capture003)
My apologies if this is common knowledge that I've missed; however, I've spent weeks finally getting this. (And I don't even visit Youtube regularly . . . it's just the "if you can do it, why can't I" frustration that needed to be pacified)
Anyway, maybe this will be helpful to someone.