Assuming you have CS5.5 installed there is a "work around" (if its worth the hassle to you. alternatively, just work in CS5.5)
1. Import the clip into CS5.5
2. Do not edit it, just export it to a folder (As Audio ONLY!)
3. Open CS6 and import the original clip into the new project. There will be no sound of course ! drop it on the time line.
4. Import the audio only file from the folder into the project. And drop it on the timeline.
If required, once on the timeline the seperate parts can be tied togother.
1. Select and highlight the parts to be linked.
2. Select "Clip" from the toolbar.
3. Select "Link".
Hopefully Adobe will address this issue in a future update. at present they dont seem to acknowledge there is a problem.