If undo doesn't work, and there's no autosave vault, then how do you fix a accidental timeline deletion?

I think you are right about waiting for Lion, which will have the 'auto save' and versioning built in. I'm concerned that you couldn't undo. Unless you closed the app in-between, that's a really big problem.

I've been hit by this flaw many times which requires me to start the project again and again!

I recovered the UNDO function.....

how?

I delete all Preferences and APP SUPPORT FILES in Library regarding to Final Cut....

Regards....

I also experienced the disabled Undo/Redo thing after trying some Transform and keyframed stuff on some clips. I got very frustrated. So after a couple of hours I gave up set FCPX to Transcode all my vids that I was working on, and went to bed. The next morning I quit and restarted FCPX and my Undo and Redo worked fine and so far still does. I redid all the same Transforms, and all was saved.

Now I could be wrong (cross my fingers; this is my hunch); FCPX may only be able to autosave (and thus Undo & Redo) footage on which you perform alterations or special effects once said footage is fully Transcoded. Perhaps someone at Apple can confirm this.

Good luck everyone...

Not so. You can effect native material and the undo does not disappear. What seems to be happening is that when undo disappears autosave is off as well.

You're right. I experienced that too. But as long as I was just trimming and assembling shots in Project, all was fine. When I started doing some key-framing and transform effects, that's when the Undo/Redo (which I'm sure is linked up with autosave) bloody-well went down to Florida for a frickin' summer vacation. :-))

So I'm guessing that for more complex processing of clips FCP may require the transcoded version. It could also be that FCP was transcoding that clip at the time I was trying to work on... I dunno... But like I said, these only my guesses.

I'm now going to try and finish that 6-minute movie I've been struggling with for several days because of this bug/malfunction (?)... So far all is good. I'll keep ya all posted.

:-))

I solve this issue by deleting all preferences regarding to final cut X in

~/library/Application Support/final cut pro

~/library/Preferences/com.apple.FinalCut*

You can access these folder by following these steps

-open a new finder window

-select Go to Folder (Command + Shift + G) from the Go to menu, type in this window "~/library/"

How I discovered the solve of this issue...

I did a clean installation of lion and install all software and all nice! but... when I restore my user from time machine the problem appear again.... Them I assume that is a problem coming from upgrade to lion from snow leopard with final cut pro x installed...

Sorry for my english

Regards!