Did you install any software provided with the new camera? It may be that it has changed a codec previously used by PRE. If you did uninstall the software (or better yet use System Restore to restore to a time before adding the new software) and see if your older videos play back smoothly again.
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What type of camcorder is your video coming from?
The vast majority of the time, jerky playback (at least if you're talking about your final output video) is either the result of using a non-standard video source (like video from a still or Flip camera) or a project in which the settings aren't right for the source video.
The problem occurred prior to my new camera - and no I haven't installed anything with that except for PMB which I'm not using. Could probably uninstall anyway. I am currently using a Sony HDR-XR550VE camera but this occurred with film from my old camera as well which was a Sony DVD755E. I suspect the problem may be a result of one of the Windows XP upgrades that occur automatically - trouble is I don't know which one and how to fix it!
You have two different issues going on.
1) Your old camcorder was a DVD camcorder. You must use the DVD/Hard Drive Camcorder project preset or you will have interlacing problems, which manifest themselves as fluttery playback of your video. Which project settings did you use?
2) Your new camcorder is an AVCHD camcorder, which requires you to use the AVCHD project presets. Did you use these presets when making your video?
AVCHD is also one of the most challenging video formats to work with on a PC. It usually requires at least a quad core processor with at least 4 gigs of RAM. Does your computer have these specs?
Thanks Steve but that looks like more money to spend! I have 2 gig of ram in memory so looks like an upgrade might be in order. However I don't think that is my problem at the moment. The film I took on the original camera has only become a problem since about December. I edited a lot of other film prior to that and there isn't a problem with it. If I look at some of those films now on Adobe they are fine. The actual film I was editing that has the problem was filmed prior to the ones I have edited successfully and I haven't changed any settings on the camera.
With the new camera - the film shows perfectly when played direct through my Playstation 3 on to the Sony Bravia TV. I have been filming in the FQ mode so I can save it to a Blue Ray disc - hopefully by disc burn in the first instance. I am just off to purchase an HDMI cable that will hopefully allow this. I am going overseas in 2 weeks time and just want to get the camera set up to the best advantage for filming. Because I have the Blue Ray capacity I would really like to use that and my understanding is that even if I film in that mode I can always save it to a different mode later.
I still think that there may have been a Windows XP upgrade that has conflicted with the editing programme. I am waiting on a new programme which came with the camera so it will be interesting to see if I have the same issue.
The film I took on the original camera has only become a problem since about December.
Looking only at this aspect for a moment, two things to consider:
1.) that your Project Preset matches that camera's footage 100%. Steve addresses this above.
2.) that your video card driver is updated to the very latest (keep any older one on the system in a safe place, just in case). An OS update/hot-fix can render a video driver obsolete in a heartbeat. PrE (and most NLE's) interface much more closely with the video (and Audio) driver, than other programs, like simple AV players. It will point up issues, that other programs might overlook.
Also, have you installed any CODEC "packs," like K-Lite, or the app., FFDShow, part of K-Lite, others, or available alone? It has caused many issues with Adobe programs, and playback.
PS - also, PrE interfaces very closely with Apple's QuickTime Player, and some versions of that do not "play nice" with Adobe programs. Which version do you have?