PrePro 5.5 & Encore Hang when scale to frame

Question

I just tried to create a DVD made up of several segments taken from YouTube downloads.   I first loaded all the segments into a timeline In Premiere Pro 5.5, and for each segment I selected to scale to frame.  The segments all played fine in Premiere Pro.  However, when I used dynamic link to transfer to Encore to set up the DVD, Encore hung while it was opening the files.   I later when back to Premiere Pro and loaded each segment individually, set it to scale to frame, and then exported in DV Widescreen format.  Two of the segments worked OK.  The third one hung the Adobe Media Encoder.   I used Nero 10 Vision to scale the one that failed, then created my timeline again with the DV saved files.  Everything loaded OK in Encore except that I got an error message during the transfer something like could not locate transcode presets.  Strangely, I noticed that I now had about 19 seconds of blank space at the very begining of the timeline.  I set up the DVD anyway. It previewed fine in Encore.   However, when I tried to build the DVD, the program stopped with an error that there was an incompatable size at about 19 seconds into the timeline.   The only way I got it to work was to take all of the raw video segments, scale them to DV wide size using Nero 10 Vision, then created the timeline using the Nero files.  This time, when I used dynamic link I still got the transcode preset error, but I had no gaps, and the DVD I made built OK.
I thought that Premiere Pro 5.5. was supposed to handle all the size compatabilities.   I defined the sequence in PP 5.5 as DV wide format, and (orginally) selected scale to frame for each of them.   It seems like PP must not be scaling the files correctly.  To make matters worse, whatever it does to the files can hang up (not give an error, just lock up) both Media Encorder and the transfer to Encore.   Has anyone had these issues?  Is there anything I did wrong?   Note that the segments that caused me problems were all downloaded from YouTube in .mp4 format, and they were smaller than DV in size (like 480 x 270).  Premiere Pro 5.5 would not import the flv versions, so they must have been encoded with the Sorenson Spark codex that PP 5.5. does not support.  
Thanks.

Answer 1

Thanks.   I am not that experienced and did not think about a media cache.   I will try that the next time.  However, I was trying to get them all to the DV resolution (I know one loses something on scale up) because I understand that is required for a DVD.