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It's never a good sign when the top two hits on Google are your post!  doesn't look like a common error.

No idea, but when faced with an uncommon error, that persists after a windows restart and  Encore close/open, I start testing with a new simple project, then elements of the problematic one.

I've started experimenting with looking at windows error logs to see if they add some info about what is happening.

For CS4 you must update the Roxio component http://forums.adobe.com/thread/400484?tstart=0
More on Encore and Roxio http://forums.adobe.com/thread/528582?tstart=0 or direct to
http://kb.roxio.com/search.aspx?URL=/content/kb/General%20Information/ 000070GN&PARAMS 

Plus, Long File Names or odd characters Cause Crashing http://forums.adobe.com/thread/588273
And #4 Here http://forums.adobe.com/thread/666558?tstart=0
And This Message Thread http://forums.adobe.com/thread/665641?tstart=0 

An Encore Tutorial http://www.precomposed.com/blog/2009/05/encore-tutorial/

I just got the same error.. First time I've ever had it..    This is disc 3 of a 5 disc set I'm doing,  none of the others have come up with this error..  I'm burning to DL DVD.. Will try again now, see what happens..

^   FYI....

Unusual error combined with works on one disk, not another = Do Over. That is what worked for him this time anyway.

Dual layer requires running as administrator, but again, your other ones worked.

In any event, I suspect corrupted project, and would work through these if it is a complex project and a do over is difficult.

Troubleshoot damaged projects in Encore on Windows

http://kb2.adobe.com/cps/406/kb406006.html

I've got a little further information on this.. It hasn't helped, but it's further information -  there doesn't seem to be anything out there..
Maybe Adobe can start putting pieces together..

I've cleared the cache..  
I've started a new Encore project (via dynamic link in Prem) and tried to burn a basic 1 menu, I button/link disc.. 

This failed - right at the end..

I tried the 'transcode now' feature in Encore - it worked on the very short timeline, but the main timeline which is about 1h:45m long failed right at the very end..

I'm currently trying another disc (project) to rule out an issue with the computer/software..   Tomorrow, I'll be trying this failed one on a mate's Mac (I'm on PC).

I REALLY don't want to have to re-do this project..

Did not go back to read your earlier post: if you have not tried to export from PR, rather than dynamic link, that may be an option.

You want to export as MPEG2-DVD, with a size setting so that Encore will not retranscode.

If your timelines are the same length as other disks, you can look at what Encore picked for them. Otherwise, use a bitrate calculator.

Excellent!

Theoretically, either cache should work (the cache is common), but...

Thanks for letting us know. It is always tempting to think the regular things won't work, and I'll bet that clearing the cache from PR is not one that is often tried.