I also discovered this behavior last summer. Unfortunately the best (lame) answer I could find was that "Some formats, such as Long GOP based media files, cannot trim media, or add handles." Source: http://help.adobe.com/en_US/premierepro/cs/using/WS1c9bc5c2e465a58a91cf0b1038518aef7-7c72a .html
That's not very specific, but in my case at least (and it sounds like in your case, too) .MXF may be another file type that cannot be trimmed. If I remember correctly, the answers I got from others was that they were able to export fine. My machine (and maybe yours) has an issue that nobody else seems to have encountered. So none of the prescribed remedies allowed me to move forward in this regard.
After much searching, asking and several suggestions from various Premiere communities, I gave up and moved on.
Use Remove Unused and then Collect Files and Copy to New Location. At least that can help you if you have a lot of clips. In my case, it didn't help much, because my very short clips were edited from very long takes, so as Premiere sees it, not much was "unused".
Be aware that "Project Manager does not copy and collect After Effects compositions that are dynamically linked to an Adobe Premiere Pro project. Project Manager does save the Dynamic Link clip in the trimmed project as an offline clip, however."
Wish I could offer you more.
CSCooper, thanks for your prompt reply.
I think you have cut to the crux of this issue, being that Premiere CS6 doesn’t know how to top'n tail .MXF files.
I would however like to restate 4 things
1) Premiere CS5.5 Created New Trimmed Projects just fine! So this is something that’s happened with CS6.
2) The same thing happens on my home iMac OS X Lion running Premiere CS6, (so it's not just our Intel i7 2600k DQ67SW machines running Win7 Enterprise 64bit.)
3) The length of the .MXF file makes no difference, it crashes with a single file shorter than 12 frames.
4) Why are there so few users complaining about this? Does no one consolidate their projects using the "Create New Trimmed Project" function?
I have in the meantime told the Lecturer concerned to "Hope for the best and expect the worst" and to proceed using your suggestion of 'Remove Unused and then Collect Files and Copy to New Location".
Thanks again for your help on this matter.
I have Premiere CS6 which does trim MXF beautifully (but only after I unlink and delete mxf audio from timeline).
My collegue has Premiere CS6 which doesn't trim MXF, just copies all footage (using same source, same project, same settings, same everything)
I also have Premiere CC installed, which also doesn't trim MXF, just copies all instead.
What the heck, Adobe?