I have had similar issues exporting H264 or really anything for that matter other than ‘same as source’ directly out of Avid. The work around I’ve come up with to create H264 files for the web is to ‘File’>> ‘Send To’>> ‘Sorenson Squeeze’. When the prompt box opens for sorenson, I click ‘options’ next to ‘Sorenson Squeeze Export 1’. In these options you can set your H264 parameters, kbit rate etc. After clicking ‘ok’ Avid will start exporting, just be sure you know where your new file will be saved. When it’s done Sorenson will open with the H264 file loaded. I close Sorenson ASAP, and grab my H264, usually saved to the desktop, and transfer elsewhere.
Depending on what type of media you have in your sequence, you might require video/audio mixdowns before export. Any time I have long GOP media mixed with something else I find a video mixdown often save headache when it comes time to export.
I’ve tried these exports on Squeeze too, but the application seems to fail no matter what I’m attempting to squeeze.
Good luck,
Lindsay