I'll buy you a drink if the frames have been dropped. You're most likely rendering to an uncompressed codec that was not designed for real time playback but is used to preserve every bit of pixel data for further processing. The frames are not being dropped, your system just isn't able to playback that much data without problems. To playback uncompressed HD you'll need at least a large drive array.
Try rendering your entire Premiere timeline. You could also try rendering in AE to something like PhotoJpg QT with quality at 95% or, for playback not further production, render to a playback codec using the Adobe Media Encoder and any of the default settings available there for playback.
Maybe I should have explained myself clearer, I am rendering as uncompressed AVI then placing this in a new AE comp and rendering into h.264. I've used this method many times to save on re-rendering times for large jobs (cleints always want tweaks), this problem has never appeared before. The glitches I am seeing are single frames, half drawn, with black covering between 10-90% of the frame. They begin to appear in the most complex area of the video and continue intermittently after that, this leads me to believe the problem is something to do with my computer becoming overworked during render process.
Thanks for the replies so far, any further help would be greatly appreciated
How are you rendering to H264? You should be using the Adobe Media Encoder directly or rendering to a lossless or nearly lossless codec and then using the ME or some other 3rd party app. Going directly to H264 from AE is a bad idea especially if some of your sources are interlaced.
I'm importing the lossless AVI back into the AE project, placing it into a composition and rendering that using the render que into h264. Could this be causing the problem?
When I RAM preview the video file in the composition I can see the glitches, and I can isolate them in the timeline, they're easily fixed with Time Remapping but it takes quite a lot of time to isolate and fix them all.
I'm not sure of the specifics of interlaced-ness, but if it helps, all the elements of the original video (before I've converted to AVI) are vector based text and shapes or still bitmap images.
Do I need a more powerful computer, my current machine is a 64-bit HP laptop (running 64-bit AE), Intel Core i5, 2.27GHz, 4GB of ram, I'd have thought that'd be enough.
I'd certainly recommend more memory. In 64-bit AE, 4 gigs doesn't go very far. It's a cinch you can't use multiprocessing, so if it's not turned off already, you should do so now.
Likewise, the possibility exists you might be using Open GL to accelerate rendering, and that rarely -- if ever -- works well. I recommend turning Open GL off for rendering as well.